Whassup in the Milky Way?

Hunting Himalia - Part One

2011-12-10T15:33:00.018-07:00

It was a super autumn here in the wild west, restorative you might say.

After the brutal spring winds that started unseasonably early in February and finished unseasonably late in May—accompanied by drifts of choking smoke from the catastrophic Wallow fire in Arizona—I was fall-to-my-knees grateful for clean, fresh fall air, accompanied only by fragrant drifts of roasting New Mexico green chile. After the blistering heat of our first summer on the mesa—and the challenges of trying to stay cool in a minimally insulated outbuilding masquerading as a residence—the crisp, cool autumn air was invigorating. After more than a few dark days of doubt, I am again filled with hope for my homesteading adventure.

Bolstering my restored optimism are systems that are finally beginning to work as envisioned. We sorted out the problems with our photovoltaic system and are now powered 24/7 by our nearest and dearest star, the Sun. We acquired a full-size propane refrigerator, so no more cooler runs to the ice machine in town, a 30-mile roundtrip. Even the cell phone service at our homestead miraculously and mysteriously returned this fall, after going AWOL for four months.

Our propane generator has been repaired and works like a top; we use it for our occasional heavy power loads. Such as, tada, pumping water! That’s right, we’ve fired up the well pump and filled our water tank. After having our H2O tested for E coli and nitrates (it passed with flying colors), we drank deep from the aquifer deep.

Water flows for the first time at the homestead

Nope, no flush toilet yet, but we’re almost there. The holes were dug, the tank acquired, the permit signed off on, and then the John Deere tractor broke down. Machines rule. We need it both to set the tank in the hole and to fill the leach field with river rock. We acquired the tractor second-hand, and although nothing runs like a Deere, the previous owner did only the minimum maintenance required to keep it running. It’s been in the shop for a month as the mechanics give it a complete overhaul, disassemble each system, revise and re-revise the initial estimate, and order in more parts. My foot is tapping compulsively. Can’t they work any faster? Don’t they know they’re standing between me and the realization of my flush toilet pipe dream?

*****

Speaking of dreams realized, this enchanted autumn I fulfilled 50% of my 2011 New Year’s Stargazing Resolutions. Okay fine, there are only two items on the list, but they’re tough ones.

My first resolution was to observe Himalia, the so-called “fifth moon of Jupiter.” Anyone who’s looked at Jupiter with even a decent pair of binoculars has seen the four Galilean moons, the moons discovered by Galileo in the early 1600s: Ganymede, Io, Callisto, and Europa. The bright, star-like dots are easily apparent as they orbit the planet, arranging and re-arranging themselves in different configurations.

Well, Himalia is Number Five, reportedly the only other of Jupiter’s 60-plus moons that can be observed by amateur astronomers. It’s tiny, and recovering the faint speck would be a challenge requiring a bit of preparation and a substantial telescope. No one I knew, even veteran observers, had seen it, which made it irresistible as an observing target.

Like the Galilean moons, Himalia is named for one of the mythological Zeus’s (Jupiter’s) romantic conquests; the nymph Himalia, seduced by Zeus when he visited her native island of Rhodes, bore him three sons. The moon Himalia is about 100 miles in diameter; compare that to the smallest of the Galilean moons, Europa, which is 975 miles in diameter. I didn’t know if I had the observing chops to spot a 15th-magnitude (really really faint) flea-speck 400 million miles away in outer space, but I was on fire to try.

The highest resolution image available of Himalia
Image source: NASA, New Horizons mission to Pluto

When the stormy summer skies gave way to azure days and inky black nights, and Jupiter returned to the eastern sky after sunset, I knew my window of opportunity had arrived. I began my quest by reading amateur astronomer Rick Scott’s invaluable how-to article.

His six-step approach was a bit daunting, however, and involved the purchase of a couple software aps, so I only did Steps #1 and #2 in preparation. I figured I would see how far I could get, and re-group if unsuccessful.

Step #1
I went to the JPL Horizons site to generate an ephemeris. An ephemeris is a table showing the position of a celestial body for regular intervals. This data would tell me precisely where in the sky Himalia would be at specific times so I could target the telescope correctly. On the input screen, I changed Target Body to Himalia, and Observer Location to the closest town to my location.

For Time Span, I first had to determine what time I wanted to start looking for Himalia. I wanted Jupiter to be fairly high in the sky because observing conditions are generally best when an object is high in your sky (you’re looking through less of Earth’s murky atmosphere overhead). So for that night, I settled on midnight. Since all astronomical events are expressed in Universal Time (UT), you need to be familiar with how your time zone converts into UT, so you can interpret the ephemeris when it spits out.

I inputted the following day’s date for Start Time, and the next day’s date for Stop Time, and selected “1 hour” for Step Size. This would give me a 24-hour ephemeris at 1-hour increments, more than what I needed, but spanning my planned observing time. A click on the “Generate Ephemeris” button, and Bob’s your uncle. Here’s what it looked like:

Step #2
Next, off to the Digitized Sky Survey (DSS) site to pull an image of the piece of sky I’d be looking at. This would tell me what stars lie in the field of view where I’d be looking for Himalia. Since the moon would be in motion and just passing through the star field, I could expect to see a “star” that shouldn’t be in that field, once I began observing.

Astronomers use a celestial coordinate system—a sky-grid, if you will—to pinpoint the location of celestial objects, as seen from Earth. Each object has a Right Ascension (RA) coordinate and a Declination (DEC) coordinate. I had the RA and DEC for Himalia listed on my ephemeris, for each hour. I knew that 12 midnight in my local time converted to 6:00 UT, so I transferred the RA and DEC coordinates listed for the 6:00 time slot into the DSS search form. I selected HST Phase 2 (GSC 1) in the Retrieve From field. For File Format, I selected GIF. For Height and Width, I retained the default setting, to generate an image 15 arcminutes by 15 arcminutes. The image would be oriented with the RA and DEC for Himalia dead center. A click of the "Retrieve Image" button, and I was able to view and print this image of my hunting ground.

The starfield where I would hunt for Himalia

I had secured my two key pieces of supporting documentation to take to the observing field. Just two more important preparation tasks remained before lift-off. Stay tuned for the exciting conclusion, in my next post.

Heavenly Waters

2011-08-14T23:36:00.023-06:00

At the off-the-grid DIY homestead where I have staked my corner of paradise, all things proceed at the breakneck pace of a banana slug, and any piece of equipment may break or blow up at any given time.

Five months after turning my back on civilization, I take stock and find myself living in a 200-square-foot building with a spousal unit, four rescue cats, a part-time jury-rigged power system, a postage-stamp-sized RV fridge that reliably spoils milk, a cell phone that can’t pick up a signal unless I drive a mile away (and which is “supported” by technicians who can’t even find our property), and no running water. Think Beverly Hillbillies, before the oil strike.

Why (you may ask in a horrified tone of voice) would any sane woman choose to live this way? Simply put, my mate and I are stargazers, avid amateur astronomers who need dark skies to pursue our passion. We have staked our claim at the side of the road-less-travelled because that’s where we can escape the light pollution that has taken over the night sky above cities, suburbs, and even semi-rural areas. It’s a straightforward equation really:

No neighbors = No line-of-sight lights

At the drop of a hat, we can go outside, throw up a telescope or grab a pair of binoculars, and be ready to visit the bright lights of our home galaxy, the Milky Way: planets, globular clusters, nebulas, and brilliantly colored stars. Not to mention entire other galaxies far far away.

Living in the high desert—with its reliably transparent, steady skies—is how we ensure maximum access to our celestial playground. If skies are cloudy and don’t clear up until after midnight, no problem. There are no cars to load with equipment and no middle-of-the-night expeditions to get to an acceptably dark site. We simply wait it out like patient game hunters, and pounce when the stars emerge. We don’t even have to change from our camouflage-print pajamas if we don’t want to.

*****

Desert dwellers understand better than most what it means to do without. (Have I mentioned we have no running water?) When you choose to live among arid grasslands atop a windswept mesa in middle-of-nowhere New Mexico, water is a luxury and becomes more precious to you than the Hope Diamond, the Koh-i-Noor, and the Great Star of Africa combined. A girl’s best friend, as it turns out, is a flush toilet.

In this poverty of creature comforts, water seems like something from the realm of myth and magic: something that surely could be conjured if only I knew the right incantation. It flows unseen beneath my feet at a depth equivalent to the height of a 52-story skyscraper. In our well casing—or Big Drinking Straw, as I like to think of it—hangs a three-horsepower pump and enough copper wire to send ripples through the commodities markets. Sadly, can’t start a fire without a spark. The propane generator—a.k.a. Big Spark-Maker—sits silent, broken by a careless contractor and waiting for a replacement part that surely must be coming by stagecoach.

Water gathers unseen above, also. After a brutally dry and windy spring and early summer, the monsoons have finally arrived. Spectacular thunderheads, laden with moisture from the Gulf of Mexico and the eastern Pacific Ocean, travel northward from Mexico, bringing the summer rains that represent up to 70% of New Mexico’s annual precipitation.

We watch the storms’ northward progress with equal measures of hope and cynicism. Often they simply break apart on the southern prow of our ship-like mesa, dumping their juicy payloads in the river valleys on either side. Our skin cracks like the tessellated adobe soil lying just under the blow sand. We grow as leathery as the resident collared lizards.

Occasionally, though, the rain clouds sail straight overhead and we receive a direct hit. Recently, like tears of joy, a half-inch pelted the parched earth, the thirsty mesquites and junipers, the dusty cattle, and all the enduring creatures of land and air.

That night, a strange sound came to me in the dark from across the mesa. It took me a few minutes to pin it down: a chorus of frogs, harmonizing. Frogs in the desert! How long had those recondite amphibians burrowed in the desert floor, waiting for the elixir of rain? How many generations ago had their ancestors shipwrecked on this desert island, when the inland ocean receded?

*****

Any good Southwestern stargazer knows that a freshly-scrubbed, transparent sky follows monsoon rain. Freshly-scrubbed. Gee, that sounds good. Did I mention we have no running water? But I digress.

Tonight I looked for omens of water in the sky. The Moon rose shortly after sunset, and its nearly full face was filled with large dark splotches called maria (MAH-ree-yuh) or seas, easily seen with the naked eye. Their watery name derives from an early belief that they were bodies of water, lunar oceans. We now know they’re craters that filled with lava when the Moon was volcanically active. I tick off their names like charms: Sea of Serenity, Sea of Tranquility, Sea of Fertility, and my new favorite, Sea of Rains.

I find that when the Moon is close to full (in this case, one day after) with most of its face illuminated, it’s easier on the naked eyes to look at it before the sky gets dark. I can see more surface features when its brightness is muted against the blue sky of twilight. But when the sky grows dark, whammo, the Moon becomes as blinding as a searchlight and hard to look at. Check this out for yourself on or near any Full Moon that rises when the sky is still light.

Is it an especially good omen that tonight the Moon was in the constellation Aquarius the Water Bearer? While I take a moment to imagine myself standing in the endless stream of water flowing from his jar, enjoy this portrayal of Aquarius from John Flamsteed’s 1729 star atlas:

Courtesy of Linda Hall Library of Science, Engineering and Technology

A few hours after sunset, I spy the star Fomalhaut (FOAM-uh-lott) in the southeastern sky. The brightest star in the constellation Piscis Austrinus the Southern Fish, Fomalhaut shines through even in a sky washed out by moonlight. From the Arabic for mouth of the fish, Fomalhaut marks the open mouth of the rather thirsty fish, into which pours the cool stream from the Water Bearer’s jar. Heavenly.

March Madness

2011-03-19T12:36:00.005-06:00

Greetings, sky-watchers! Please forgive my multi-month absence, but I had the best of reasons. I was moving to a locale with significantly darker skies--an observer's dream come true.

This year, my blogging focus will be on "current events," that is, to inform you of neat celestial events happening in the present or the very near future, as well as to recommend objects for you to look at in your current sky.

It's an eventful time in the sky right now--starting tonight!

1) Just after sunset tonight, look west. As the sunset glow recedes, the first objects you'll see pop out low in the western sky will be two planets. The brighter one is Jupiter. It will be about one fist-width above the horizon. Make a fist and hold it at arm's length against the sky. Measure across the knuckles to approximate a fist-width. About half a fist-width above Jupiter is Mercury, not nearly as bright as Jupiter and pinkish in color. NASA's Messenger spacecraft just this week entered orbit around Mercury--a first in space exploration. We can expect to learn a lot more about this sun-drenched planet in the next year.

You can see the planetary pair for the next few days, after which Jupiter will disappear below the western horizon. Mercury will be do-able for a few more nights, but as we head towards month's end, you'll probably need binoculars to pick Mercury out of the twilight.

2) Tonight about a half hour after sunset, look east to watch the Full Moon rise. This is the "super-perigee moon," the biggest Full Moon in nearly 20 years. It will be in the sky all night, so you'll have plenty of time to gaze upon it.

Why is it so big? The Moon’s orbit around Earth is oval-shaped, with one narrow part of the oval about 30,000 miles closer to Earth. At its closest to Earth, the Moon is said to be at perigee; at its farthest, at apogee. Full Moons that occur near perigee are the biggest and brightest, about 14% bigger and 30% brighter than “apogee moons.” Tonight, the Full Moon occurs a mere one hour from perigee!

Note: the Moon is not closer than it's been in 20 years. I've been hearing this a lot on TV and other media, and hearing people repeating it. The Moon draws close to Earth every perigee, and perigee occurs once every 28 days. It would, however, be correct to say that the Full Moon is closer than it's been in nearly 20 years, because normally the Full Moon does not coincide so closely with perigee.

3) Tomorrow, Sunday, March 20, at 5:21 pm Mountain Time (adjust for your time zone), we celebrate the moment of the Spring Equinox or Vernal Equinox. By convention, this event marks the beginning of the season we call "spring" in the Northern Hemisphere. The Spring Equinox is when the Sun crosses the celestial equator (where the plane of Earth’s equator would intersect the sky), heading north. On the Equinox, the Sun rises due east and sets due west, so you can use this opportunity to mark west and east at your location, using natural or man-made markers on your horizons. (Caution: To protect your eyesight, never look directly at the Sun!)

Until next time, happy star trails to you.

Jumpin' Geminids!

2010-12-09T20:42:00.012-07:00

In the wee hours of Tuesday morning, December 14, the Geminid meteor shower will peak. This is a great opportunity to view one of the more reliable meteor showers of the year, if you're an early riser or if you don't have to work on Tuesday.

I fall into the latter category, which is a good thing, since I'm far more adept at staying up than at getting up. I plan to begin viewing after midnight, since a big old waxing (growing) gibbous Moon will light up the sky until around 12:45 a.m. Bright moonlight is a meteor watcher's nemesis, as its glare washes out many of the fainter meteors.

This shower's radiant--the point in the sky from which the meteors appear to emanate--lies in the constellation Gemini, which will be at its highest point in the sky between 1 a.m. and 2 a.m. local time. Geminids can appear anywhere in the sky; if you spot a meteor during this hour and can trace its trajectory back to a spot overhead, chances are it was a Geminid.

Geminids usually appear white or yellow, and we'll have a chance to spot some really bright fireballs. There should be around 120 meteors per hour "jumping" at the shower's peak.

The best viewing position for meteor watching is lying down, so you can see the largest amount of sky at once. You have a better chance of spotting the most meteors this way. I plan to lie on a comfy chaise lounge inside a down sleeping bag. Yes, the Geminids are a great shower but do they have to fly during the coldest month of the year in my area?? A thermos of hot chocolate within reach is also on my must-have winter meteor watching list.

Here's hoping for clear skies on Tuesday morning in your area. Good luck, and be sure to post your Geminid-watching experience here.

Honk If You Love the Heliosphere

2010-11-25T23:30:00.012-07:00

I’ve heard that there’s a point, marked by turbulence, that marks the edge of the solar system as a satellite passes out of it. What causes the turbulence? What is out there to be turbulent? ~Matt

Racing from the Sun in all directions at about a million miles per hour, the solar wind is a stream of electrically charged particles. The solar wind, carrying with it the Sun’s magnetic field, forms an enormous magnetic “bubble” called the heliosphere that encases the solar system. This protective bubble shields our solar system and planet from (some but not all) harmful cosmic rays, high-energy particles traveling through space. We heart the heliosphere!

The transition zone where the solar wind meets the interstellar medium, the thin gas and dust that exists between stars, is called the heliopause. Here at the outer edges of the heliosphere, the solar wind mixes with the interstellar medium; this interaction between two different densities and pressures creates turbulence.

The Heliosphere and the Voyager Spacecrafts
Courtesy NASA/JPL-Caltech

When the solar wind approaches the heliopause, it slows very abruptly, causing a shock wave to form. The shock wave is called the termination shock, and this boundary is marked by dramatic changes in magnetism and temperature.

NASA’s Voyager 2 spacecraft crossed the termination shock in 2007; Voyager 1 had crossed it three years earlier in 2004. And here’s a funny twist: Voyager 1 only had to cross the termination shock once; Voyager 2 had to cross it five times! This occurred because the heliosphere bubble flexes in response to solar flares and other ejections of material from the Sun. In this case, the termination shock became a moving finish line.

Voyager 1, launched in 1977 and now ten-billion-plus miles from Earth, is the most distant of all active spacecraft. Voyager 2, which launched a few weeks earlier than Voyager 1, is only eight-billion-plus miles from Earth. This lag exists because Voyager 2 took a little planetary side tour. It began heading out of the solar system nine years later than Voyager 1, after becoming the first spacecraft to observe Uranus and Neptune.

In about five years, Voyager 1 will leave the heliosphere behind and enter interstellar space; Voyager 2 a few years after that, each spacecraft heading in a different direction. What new wonders will these stalwart space voyagers encounter, in the realm beyond the Sun? Stay tuned.

How Far Can We See? (part two)

2010-11-11T23:50:00.021-07:00

Now for the exciting conclusion--and the second answer--to Matt's question of last week, which you may recall was:

"Is there a specific star that represents the farthest a person can see with the naked eye?"

Although the Andromeda Galaxy is the farthest object the average person can see with the naked eye, there is a star that is reportedly the most distant that can be seen naked-eye. It's a variable star in the constellation Cassiopeia the Queen, and it has the unromantic name of V762 Cas.

A variable star is a star that periodically brightens and dims. In the case of V762 Cas, it's most likely doing that because it's in a red supergiant phase, and it's begun to swell and shrink. A red supergiant is approaching the end of its life. It has burned up all its hydrogen fuel, and has begun burning other elements in a specific sequence. This causes rather dramatic changes in the star's size, temperature, and "behavior."

Image from Palomar Observatory Sky Survey

V762 Cas lies about 15,000 light years away. As we learned last week, one light year is nearly six trillion miles. Now multiply that by 15,000, take two aspirin, and go lie down.

V762 Cas must be a big honkin' supergiant, if it's that far away and we can still see it, yes? Unfortunately, I have not yet been able to spot V762. It is right on the outer limits of naked-eye accessibility, so I need to try again at a really dark site. Acquiring this sort of faint target, along with a faint target like the Andromeda Galaxy, benefit greatly from an effort to properly dark adapt (see last week's post).

To give it a try yourself, face north and locate the Lazy W asterism of Cassiopeia, which looks like a W or an M, depending on its orientation when you look. Download a free sky map for the month at http://www.skymaps.com/, if you don't know how to locate Cassiopeia.

Now draw an imaginary line between the star at the roof peak of the House asterism of Cepheus--it looks like a child's drawing of a house--and the leftmost star of the Lazy W, if it were oriented as a right-side-up W. V762 lies on that line. The star map below will help you pinpoint its location.

Looking north toward Cassiopeia and Cepheus

If you have success spotting it, please post your results in the Comments. Also, if you can spot it with binoculars or a telescope, let us know that also; I'm curious to know if anyone sees any color in the magnified image. Sometimes color is significantly enhanced with a little magnification.

Good luck to us all!

How Far Can We See? (part one)

2010-11-04T21:01:00.015-06:00

Astronomy enthusiast Matt, whose favorite celestial object is the three-star asterism (recognizable star pattern) Orion’s Belt, dropped quite a few questions into the Ask An Astronomer box. We’ll start with this one, since it’s perfectly timed for autumn stargazing:

“Is there a specific star that represents the farthest a person can see with the naked eye?”

I love this question, because it has two answers. First, the most distant object that a person with average eyesight can see with the naked eye is…
...not a star! It’s a galaxy, specifically, the Andromeda Galaxy.

Originally called the Great Andromeda Nebula, it became known as the Andromeda Galaxy after the famous astronomer Edwin Hubble confirmed its galactic nature in the 1920s. At an estimated 2.5 million light years away, it’s the nearest spiral galaxy to our Milky Way. The Andromeda Galaxy is more or less comparable to our home galaxy in size and mass, but astronomers believe it has a significantly higher star count.

Keep in mind that one light year is nearly six trillion miles, so the distance to the Andromeda Galaxy is pretty hard for us to wrap our heads around. But amazingly, with a little bit of effort, we can see it! Let’s gaze.

1) You’ll need a dark site, away from city lights, to see this “faint fuzzy.” Before beginning your hunt, be sure to dark adapt to maximize the acuity of your night vision. To dark adapt, simply avoid all white light for 20 minutes before stargazing. Then use a red flashlight during your stargazing session, to maintain your dark adaptation.

2) About one hour after sunset, face east. Look well above the eastern horizon for a large, four-star square. Each side of the square is about two fists wide, if you hold your fist at arm’s length against the sky and measure across the knuckles. This is the asterism called the Great Square of Pegasus.

Star maps created with Your Sky

3) Next, find the Chains of Andromeda, the two strands of stars that arc to the left (north) of the star that marks the Square’s lower left corner. Now look above the middle star of the upper chain for a faint, fuzzy patch. A Persian astronomer of the 10th century called it the “little cloud,” an apt description. If you spot it, you’re gazing upon a collection of about one trillion gravitationally-bound stars, what the farsighted philosopher Immanuel Kant called an island universe.

If you can’t see it, you may need to try again at a darker site with less light pollution. Additionally, your sky transparency, or atmospheric clarity, may be negatively impacted by the presence of clouds, haze, dust, or humidity. If this is the case, try again when conditions are improved.

When you look up at the night sky, every star you see is in the Milky Way. The exciting thing about spotting the Andromeda Galaxy—in addition to it being the farthest object you can see naked eye—is that you’re seeing a world beyond your galactic neighborhood. That’s right, it ain’t local.

For the second answer to Matt’s fine question, tune in next week. And until then, happy hunting.

Opposition - It's a Good Thing

2010-10-21T22:19:00.007-06:00

In everyday use, the word “opposition” has a somewhat negative connotation. But in observational astronomy, opposition is a good thing.

Each planet beyond Earth in the solar system—Mars, Jupiter, Saturn, Uranus, and Neptune—is said to be at opposition when it is opposite the Sun as seen from Earth. In other words, Sun, Earth, and outer planet are in a line, with Earth in the middle.

This happens because, moving outward from the Sun, each planet’s orbit is larger than the one before, and each planet travels slower in its orbit than the one before. Therefore, each planet takes longer to complete its orbit than any of the planets closer to the Sun.

For example, Jupiter was at opposition this past September. Since Jupiter takes longer to chug around the Sun (4,332 days) than Earth does (365 days), Earth catches up to and passes Jupiter about every 13 months, slipping between Jupiter and the Sun.

The significance of opposition to hobby astronomers is three-fold:
1) When a planet is at or near opposition, it is closer to Earth than at other points in its orbit;
2) A planet at opposition is fully illuminated by the Sun, from our vantage point on Earth; and
3) A planet at opposition is visible all night long, rising at sunset and reaching its highest point in the sky around midnight.

In short, a planet at or near opposition is close, bright, and up all night. This combination presents planetary observers with optimal viewing conditions and the opportunity to see detail on the planet’s surface they might not otherwise spot. Not to mention an excellent excuse to stay up all night, no matter what the neighbors think.

Here’s a related question recently dropped into my Ask An Astronomer box at a local science center’s evening event; it was submitted by Tara:

“Jupiter just went into its closest opposition since 1963. A site I found on the internet said it wouldn’t be this close again until 2022. Why the uneven time difference if this is true?”

Wonderful question and observation, Tara. And you need know but one thing to understand why: the orbits of the planets are not perfect circles. Instead, planetary orbits are elliptical, or oval. The eccentricity of each planet’s elliptical orbit differs, that is, the degree to which the oval is stretched out from the circular. In addition, the planets’ orbits are inclined, or tilted, with respect to the plane of Earth’s orbit around the Sun. These variables inserted into the distance-at-opposition equation mean the possible distances separating Earth and another planet when they rendezvous at opposition are, well, astronomical.

The Kids Are Far Out - part three

2010-09-23T23:50:00.009-06:00

The final set of questions from the kids of Cosmic Carnival may be last, but they’re certainly not least. In fact, I think these three budding scientists asked questions which we should all consider. To do so is to begin to have some understanding of our place in the universe.

Ryan from Albuquerque, age 9, pondered this:

“I was wondering how thick the atmosphere is on Earth.”

A real brain teaser of a question, Ryan! There is no straightforward answer to this question because our atmosphere does not have clearly defined borders. As we go up in altitude, Earth’s atmosphere very gradually becomes thinner and thinner until it merges with outer space. So we could say the answer is 800 miles thick if we include the outermost layer, the exosphere, where the air is extremely thin.

Or we could use the altitude where space is officially considered to begin: 62 miles (100 kilometers) above sea level. So, the answer could also be 62 miles thick, since around 99% of the mass of our atmosphere is found below this point. You can read more about Earth’s atmosphere here.

The layers of Earth's atmosphere, bottom to top:
Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere

Image source: NOAA/National Weather Service

Scott from Rio Rancho, age 8, posed this question:

“How does the Earth spin around the Sun?”

Scott, we generally say that Earth spins (or rotates) on its axis, the way a top spins. We also say it orbits (or revolves) around the Sun. 24 hours a day, 7 days a week, our home planet is spinning like a top and traveling in an orbit around the Sun, at the same time.

Whenever you look east (the direction of the rising Sun), you are looking in the direction toward which the Earth is spinning, as well as the direction in which Earth is traveling as it circles the Sun.

Sophie from Albuquerque, age 9, was looking way beyond the solar system when she asked:

“If we’re in the Milky Way, how do we have pictures of the Milky Way?”

It’s a puzzle, isn’t it, Sophie? It’s true: we do reside in the Milky Way galaxy. In fact, every star you see in the night sky is in the Milky Way galaxy.

If you go stargazing out in the country, away from city lights, you will probably see what looks like a long, glowing cloud arching overhead from horizon to horizon. It’s actually a collection of billions of stars too numerous and faint to be resolved (separated into distinct points of light) with the naked eye, so we see it as a hazy band of light. We call this object the “Milky Way” too, even though it’s just part of our home galaxy. This is probably what you have seen in photographs, as it’s a popular target for astrophotographers.

The glowing “cloud” is an edge-wise view of the star-packed spiral arms of our platter-shaped galaxy. Even though we are in one of those arms (the Orion Arm), we can look across space at neighboring arms. The diagram below will give you a better picture of your place in space.

Diagram of the spiral arms of the Milky Way

Image source: Richard Powell

In conclusion, I have to admit that I seriously doubt I could have formulated any of these questions at the tender age of 8 or 9. I was a science ignoramus for my entire childhood and, indeed, much of my adult life. So, I am awed and inspired by the far-out kids I met at Cosmic Carnival, who are already looking up and wondering about the universe in which they live. I hope they never lose that sense of wonder.

Have you looked?

The Kids Are Far Out - part two

2010-09-16T21:30:00.011-06:00

As a rule, kids like planets, and the kids at the recent Cosmic Carnival event were no exception.

Phillip from Albuquerque, age 8, commented on his favorite planet:

“I like Neptune because I think there might be life there.”

Phillip, that’s as good a reason to like a planet as I’ve ever heard! Wouldn’t it be exciting to discover evidence of extraterrestrial life in our own solar system?

Neptune
Image source: NASA

Along with Jupiter, Saturn, and Uranus, Neptune is one of the gas giant planets, which means it has no solid surface on which we could walk. Its thick atmosphere has 1,000-mile-an-hour winds and a bone-chilling temperature of minus 350 degrees Fahrenheit. Brrrrr! Beneath the harsh atmosphere is a hot “ocean” of water, ammonia, and methane, and perhaps a small core of rock and ice.

It’s safe to say any life form that can survive on Neptune is pretty darn tough.

Julia from Rio Rancho, age 9, asked:

“Why did Jupiter become a moon?”

Thanks for your question, Julia. Jupiter is actually a planet, not a moon. In fact, Jupiter is the biggest planet in our solar system!

The planets to scale
Left to right: Outer edge of Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
Image source: NASA

A planet is a celestial body with a nearly round shape that orbits the Sun. A moon, on the other hand, is a celestial body that orbits a planet. Jupiter has over 60 moons going around it! The four largest ones were discovered by the famous Italian astronomer Galileo. You can read more about Jupiter here.

Melissa from Albuquerque, age 12, wondered:

“How long does a day last on Pluto? How long does it take for it to orbit around the Sun?”

A great pair of questions, Melissa! Although distant Pluto has been reclassified by professional astronomers as a dwarf planet, we still love it, don’t we?

A day on Pluto, that is, the time it takes for Pluto to complete one rotation around its axis, is a little more than 6 Earth days. A year on Pluto, that is, the time it takes for Pluto to complete one orbit around the Sun, is 248 Earth years.

Life on Pluto is life is the slow lane.

The Kids Are Far Out - part one

2010-09-09T21:09:00.013-06:00

To turn kids on to science and astronomy was the reason we all gathered at the annual Cosmic Carnival outreach event held at the Albuquerque International Balloon Museum this past Sunday, September 5.

The joint was jumping!

Dave Dooling of the National Solar Observatory deflates the Sun.

Len Duda of Sandia National Labs inspires a future engineer.

I met some “far out” kids (and adults) who like astronomy and stargazing, and invited them to write a comment or pose a question to be published on my blog. Liam from Albuquerque, age 10, had this to say:

“My favorite constellation is ‘o-Ryann.’ My stepsister’s name is Ryann. She is three months younger than me. Sometimes we get into arguments, but most of the time I like her. I find Orion easy to recognize.”

Ditto, Liam! That distinctive hourglass shape, along with the three diagonal Belt stars in the middle, makes Orion the Hunter quite easy to spot in the winter sky, even if you’re a beginner. Read more here.

Wow, how lucky are the kids who call Dara from Albuquerque, age 40, “Mom.” She shared this story:

“Each time we take our sons camping, they are a little older and can pick out more things in the night sky. This summer our 5 year old spent hours looking for his favorite constellation, but never found it (must be the wrong time of year for Delphinus). But we had a great time counting shooting stars and naming our own constellations.”

Right you are, Dara. The delightful little constellation of Delphinus the Dolphin leaps its way into our hearts in autumn. Starting in late September, look for it after sunset, just west of the Great Square of Pegasus. Read more here.

Finally, a young lady named Vaidehi from Lone Tree, Colorado, age 8, posed this question:

“Why do the stars change over a year?”

Excellent question, Vaidehi! Many adults don’t know the answer to that question either. So, why do we say that Orion is a “winter constellation” and Delphinus is an “autumn constellation?” And why can we see Scorpius the Scorpion in the summer, but not in the winter? In other words, why are the stars seasonal?

The Earth is in orbit around the Sun 365 days a year, right? Because we’re always moving along this path around the Sun, each night when we spin around to face the night sky, we don’t have exactly the same view we had the night before. Although it won’t be obvious to you, the night sky and its star patterns have shifted slightly to the west, or right. This is because the Earth has moved slightly eastward in its orbit, or toward the left.

This continuous westward shifting of the stars will become more noticeable to you as the months pass and seasons change. For example, you might notice that the constellations you enjoyed in summer are moving farther and farther to the west in autumn, until finally they are below the western horizon after sunset and no longer visible.

The diagram below shows an example of this, using the constellations of the zodiac. If we were standing on the Earth shown in the diagram (the black circle), at night we would look out at the constellation Pisces the Fishes. But six months later in its orbit, when Earth was on the other side of the Sun, we would look out at the constellation Virgo the Maiden at night.

Diagram by Dr. Guy Worthey

Because we’re always in motion, we’re always looking out at different “slices” of the night sky.

Why Is the Moon So Bright?

2010-09-02T22:55:00.006-06:00

The brightest object in the nighttime sky is, by far, the Moon. In fact, it can seem blindingly bright, particularly when compared to other celestial objects. With its face only half illuminated, a First Quarter or Last Quarter Moon (sometimes called a “Half Moon”) is still around 250 times brighter than the next brightest celestial object, the planet Venus.

The Moon does not emit its own light, but rather shines by reflecting light from the Sun. And as reflective surfaces go, it’s just not that impressive. The reflectivity of a body or surface is known as its albedo (al-BEE-doh), a term derived from the Latin word for white. The Moon’s albedo is around 0.12, meaning that it reflects an average of only 12 percent of the sunlight reaching its surface.

The rest of the sunlight is absorbed by the Moon’s regolith (REGG-uh-lith), the loose surface layer of broken rock and dust covering the lunar bedrock.

So, if it’s reflecting only a small fraction of the sunlight that’s striking it, why does the Moon—even a slender crescent Moon—look so darn bright? The fact is our Sun is so bright that even a fraction of its light reflected is still a lot of light. Add to that the relatively close proximity of our Moon (about a quarter of a million miles away), which gives it a large apparent size, that is, the amount of sky it covers as seen from Earth.

Now consider this: planet Earth’s albedo, or reflectivity, is 0.37. Can you imagine how bright a “Full Earth” would look if you were standing on the Moon?

Dear Mr. Horkheimer

2010-08-26T22:38:00.013-06:00

Let me be straight with you. You never were exactly my cup of tea. In fact, ten years ago, I’d never even heard of you. But then I became an avid amateur astronomer, and I learned of—and watched a few episodes of—“Star Gazer” on PBS.

I never publicly vilified you, as some did, but neither did I leap tall buildings to defend you. Let’s just say, when it comes to communicating astronomy to the general public, I’m more partial to gushing enthusiasm a la Carl Sagan than buffoonery.

Image from www.jackstargazer.com

But darn it if your campy shtick didn’t get the job done for a lot of people, as evidenced by the recent outpouring of affection, nostalgia, and starry-eyed wonder on Internet sites around the planet. Certainly you made the universe accessible to many and launched many a lifetime interest in stargazing. You championed, as I do, naked-eye astronomy, but in contrast to my little blog, you reached millions.

When it comes to showmanship, you took the cake and chewed the scenery. And, incredibly, won incredible allegiance. There’s a lesson in that for all of us who bring astronomy to the public, regardless of our respective approaches.

Here’s the thing. In reading on various web forums about your recent passing, I’ve learned that your over-the-top TV persona was a complete fabrication and a conscious choice you made. Apparently, you played it straight for many years as the “Star Hustler” (a flat-out cooler moniker, by the way) before your producer implored you to get a gimmick. I really have to respect that you did so reluctantly, and I now imagine that you may have even cringed a bit at your own antics.

After all is said and done, what we can—all of us: fans, detractors, and mere nose-wrinklers—say is that you were a good storyteller. And you made people look up. Perhaps if I had seen one of your shows 30 years ago, I would have looked up a whole lot sooner.

Now, you put me in mind of one of my favorite sayings, a message I found in a fortune cookie (where all real wisdom lies) and then taped to the computer monitor where I write:

“To avoid criticism, do nothing, say nothing, be nothing.”

You, sir, were really something.

Fire and Ice

2010-07-15T23:08:00.012-06:00

In my last post, I invited you to face west and gaze upon a gem of an asterism called the Diamond of Virgo. This time, let’s look for the fire in the ice.

Star maps created with Your Sky

First, look about midway between the stars Denebola (denn-EBB-oh-luh) in Leo the Lion and Cor Caroli (core CARE-oh-lye) in Canes Venatici the Hunting Dogs. From a dark site, you should be able to spot a naked-eye sparkly cloud. This is the Coma Star Cluster, an open cluster in the constellation Coma Berenices (KOH-mah bare-uh-NIGH-seez) aka Berenice’s Hair. An open cluster is a collection of stars that formed around the same time in the same cloud of gas and dust. About 40 stars burn brightly in this cluster. You can read more about the Coma Star Cluster and Berenice’s Hair by following this link.

Second, if you have access to a telescope (four-inch diameter or larger would be best), you can delve into the burning heart of the Diamond. Locate Vindemiatrix (vin-duh-mee-AY-tricks), a star positioned nearly equidistant from the Diamond stars Denebola and Arcturus. If you draw an imaginary line between Denebola and Arcturus, Vindemiatrix will lie slightly to the left of that line, in the direction of Spica. Vindemiatrix, which like Spica is in the constellation Virgo the Maiden, is about the same brightness as Cor Caroli.

Now point your telescope midway between Denebola and Vindemiatrix. If you’re under a good black sky and you’ve dark adapted (avoided all white light) for at least 20 minutes, you should see some little glowing smudges. Unlike the Coma Star Cluster, which lies in the Milky Way, these objects lie beyond the Milky Way. These are galaxies in the famous Virgo Cluster of Galaxies; some are brighter and easier to spot than others. Give yourself plenty of time at the eyepiece to allow the faint light from these distant galaxies to accumulate on your retinas.

A galaxy is an immense gravitationally-bound system of stars. Approximately 2,000 galaxies, gravitationally bound to one another, make up the massive Virgo Cluster. The combined gravity from that enormous collection of galaxies even exerts an influence on other galaxy groups around it, including one very important to us: the group containing our home galaxy, the Milky Way. Someday, in the very distant future, our Milky Way may find itself pulled into the Virgo Cluster to become one of its member galaxies.

Imagine the hundreds of billions of burning Suns that make up one galaxy. Now multiply that image by 2,000. That’s a whole lot of firepower.

Diamond of Virgo

2010-06-24T22:01:00.010-06:00

It has been said that diamonds are a girl’s best friend. Now any girl with her feet firmly planted on the ground knows for a fact that a girl’s best friends are Rocky Mountain Chocolate Factory truffles and control-top pantyhose.

But if I were to allow myself a brief indulgence in the alternate reality espoused by DeBeers and Tiffany’s, I would set my sights a little higher. Give me the Diamond of Virgo.

The Diamond of Virgo is a wonderful four-star, spring-into-summer asterism that, when spotted, reveals the location of four constellations. Please step into my showroom.

1) About an hour after sunset, face the western horizon, that is, toward the direction in which the sun set earlier.

Star maps created with Your Sky

2) Look high in the sky, a little towards the north, for the large, distinctive seven-star asterism (star pattern) known as the Big Dipper. In its current orientation, its handle will be sticking up above its bowl. Extend the curve of the handle in an imaginary line away from the bowl, until you reach a very bright star. This is Arcturus, the first point of our stellar diamond. Arcturus (ark-TOUR-uss) is an orange giant star, the brightest star in the constellation Bootes (boh-OH-teez) the Herdsman, and the fourth brightest star in the sky.

The Diamond of Virgo asterism

3) Now continue that same imaginary curving line toward the southwestern horizon until you reach the next bright star: Spica, brightest star in the constellation Virgo the Maiden and the second point of our diamond. Spica (SPY-kuh) is a blue-white dwarf star, and not as bright as Arcturus. Take a moment to compare Spica to Arcturus in order to see the subtle color difference. Can you discern the orange or golden color of Arcturus now, as compared to the blue to blue-white light streaming from Spica?

4) Below Arcturus and Spica, that is, closer to the western horizon, look for the shape of the constellation Leo the Lion. Our fearless feline dives after the setting sun. His head is marked by the Sickle asterism, which looks like a backwards question mark. His tail, higher in the sky than the head, is marked by a right-triangle asterism. The star in the right triangle that is highest above the western horizon is Denebola, the third star in our celestial gemstone. Denebola (denn-EBB-oh-luh) is a white dwarf star, and it’s dimmer than either Arcturus or Spica.

5) Mining our sky diamond has been fairly easy up to now. The fourth and final star is the most challenging, because it’s dimmer than the other three.

Our quarry is Cor Caroli (core CARE-oh-lye), brightest star in the constellation Canes Venatici (KAY-neez vee-NATT-uh-sigh). It lies to the right (or north) of the other three diamond points, and it lies between Spica and the handle of the Big Dipper, closer to the handle. To aid in finding it, draw an imaginary line between Denebola and the star at the end of the Big Dipper’s handle. That line will cross the white dwarf star Cor Caroli, which is a bit dimmer than Denebola.

If you can’t spot it, you may need to try again at a darker location, as an absence of light pollution is a big plus when hunting dimmer stars.

Cor Caroli is Latin for Heart of Charles and commemorates Charles II, King of England from 1630 to 1685. It was astronomer Edmond Halley (of Halley’s Comet fame) who honored the king—40 years after his death—with this designation, although it may have been Charles’s court physician who first suggested the heavenly namesake.

The Sickle

2010-05-27T22:09:00.011-06:00

The zodiacal constellation of Leo the Lion, prominent in the spring night sky, isn’t hard to locate, primarily because of the large, distinctive star pattern at its leading edge. This recognizable pattern, or asterism, is called the Sickle. It resembles its namesake, the old-fashioned farm implement used to harvest grain crops.

The Sickle also resembles a backwards question mark. Within its generous sweeping curve, we can easily imagine what the ancients saw: a leonine head topped with a luxurious mane. The celestial lion faces west, the direction in which he appears to advance. This stealthy westward movement as the night wears on is due to Earth’s rotation toward the east.

In the Greco-Roman constellation tradition, Leo represented the Nemean Lion, one of the beasts slain by Hercules during his Labors. The star pattern was, in fact, seen as a lion by the ancient Persians, Turks, Syrians, Jews, Babylonians, and Egyptians.

Four of the six Sickle stars have traditional names. Let’s learn them.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Star maps created with Your Sky

2) Look high in the sky, just west of the meridian. Leo strides across the heavens midway between the two bright stars Arcturus and Procyon. The Lion’s brightest star, Regulus (REGG-yoo-luss), marks the handle of the Sickle. Regulus is from the Latin for little king. Also known as the Lion’s Heart due to its placement in the imaginary lion’s body, Regulus is a blue-white dwarf star.

The stars of the Sickle

3) Moving up the Sickle from Regulus, the next star has no traditional name, so we call it Eta (AY-tuh) for its star catalog designation. Next in line is Algieba (al-JEE-buh), a naked-eye double star. The pair are giant stars, one orange and the other yellow. Can you see both component stars? You’ll need good eyes and a dark site. Or you can try splitting them with binoculars. Algieba is from the Arabic for forehead.

4) Continue on to Adhafera (ah-duh-FERR-uh), whose name is Arabic for lock of hair. Adhafera is a yellow-white giant, 200 times brighter than our Sun.

5) Next up is Rasalas (RAH-suh-luss), which is Arabic for lion’s head. Rasalas is an orange giant with an unusually high iron content. The terminal star of the Sickle has no traditional name, so we call it Epsilon for its star catalog designation.

In addition to being an easy-to-learn asterism well loved by beginning stargazers, the Sickle is the site of a reliable annual meteor shower. Every November, the famous Leonids appear to emanate from a spot in the Sickle. Although not currently producing meteor “storms” of hundreds of “shooting stars” per hour, as some of us (myself included) witnessed in 2001, the Leonids are still lovely. Come November, you’ll want to bundle up and find a dark site outside of town to view them. You can expect to see a dozen nice meteors per hour on or around the peak viewing night. Check this site for details.

When this king of the jungle roars, astronomers—both novice and veteran—sit up and take notice.

Cup of Stars

2010-05-13T22:14:00.011-06:00

In close proximity to the spring constellation of Corvus the Crow— and associated with it in myth— is the constellation of Crater the Cup (KRAY-turr). Both constellations have a central asterism (recognizable star pattern) that aids us in locating them. The Sail asterism of Corvus is the more prominent of the two. Spotting the goblet-shaped asterism nearby is a bit more challenging.

Many cultures have viewed the pattern found in Crater as a vessel: an urn, a goblet, a water bucket, a pot, a mixing bowl for wine, a bowl, or a cup associated with various gods.

Corvus, Crater, and Hydra in John Flamsteed’s 1729 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

In the Greco-Roman mythological tradition, Corvus, Crater, and adjacent constellation Hydra the Water Snake were intertwined. The crow, sent by the thirsty Apollo to fill a cup with water, was distracted by a fig tree and decided to linger there until the fruit ripened. He returned with a water snake in his claws, claiming it had caused his delay. Apollo saw through the lie and forever banished bird, cup, and water snake to the sky. To the sky!

1) An hour after sunset, face south and locate the Sail asterism of Corvus, just east of the meridian.

Looking south to the Sail of Corvus & the Goblet of Crater
Star maps created with Your Sky

2) The Goblet asterism of Crater lies just west of the Sail. With the Sail oriented upright on its mast, the Goblet appears to be tipping over toward the Sail. Can you spot it? The stars of the Goblet are dimmer than the four Sail stars and similar in brightness to the mast star, Alchiba (ull-kibb-AH). The bowl of the Goblet is larger in area than the Sail.

3) A star at the bottom of the Goblet’s base is the only one with a traditional name. The star on the right is Alkes (ALL-keess), the second brightest star in Crater. Alkes is from the Arabic for wine cup. An orange giant star, Alkes is about 80 times as luminous as our Sun.

Each time I search for the Goblet, it takes me a little while to find it. Just when I’m convinced I won’t be able to make it out, pop, there it is, a generously-sized cup of vintage starlight. So be patient. And when you find it, drink deeply. Salud!

Carpe Cosmos

2010-04-29T23:24:00.014-06:00

The universe waits for no one. Celestial events and phenomena are occurring all the time, some with more frequency than others. Astronomical objects are coming in and out of view— monthly, seasonally, cyclically.

None of these occur on your schedule or my schedule. They occur on their own schedule, on a cosmic schedule. It is up to us to make ourselves available to witness them, to be at the right place at the right time, so to speak.

You don’t necessarily need a pile of high-priced equipment to seize the cosmic moment. In fact, some of these spectacles are best viewed with the naked eye. A selection of my favorites are listed below. Pencil a few into your datebook, won’t you?

1) Total Lunar Eclipses. Lunar eclipses occur only at Full Moon. When the Sun, Earth, and Moon are aligned such that the Sun casts Earth’s shadow on the Full Moon, we experience a lunar eclipse. A lunar eclipse may be partial or total, depending upon the alignment of the three bodies. When all three line up so that the Moon is entirely within Earth’s shadow, it's called a total lunar eclipse, and the Moon turns red. Really! It’s a phenomenon that’s even visible in the city, and you won’t soon forget the eerie sight.

The next total lunar eclipse will occur on December 21, 2010. Totality begins at 12:40 a.m. Mountain Time (adjust for your time zone) and ends at 1:53 a.m. Mountain Time. It will be visible throughout North America.

You can practice with a partial lunar eclipse on June 26, 2010. This one’s pretty well placed for the continental U.S., with the exception of the East Coast. You’ll need to get up in the wee hours on the 26th and watch the Moon setting, just prior to sunrise. This is when you’ll see a portion of the Moon in shadow— at greatest eclipse, about 50 percent.

2) Meteor Showers. Comets leave behind clouds of debris when their orbits take them near the Sun. Subsequently, when Earth, on its orbit around the Sun, plows through one of these debris clouds, we experience a meteor shower.

The Perseids (PURR-see-yidds) are a reliable shower active from mid-July through the end of August. This year, they peak on the morning of August 12, 2010. The peak date, as well as a day before and a day after, are all good times to plan to view them. You’ll need to watch for them between midnight and dawn. This year should be optimum viewing, as the waxing crescent Moon will set before midnight and therefore won’t wash out the sky.

You won’t see many “shooting stars” in the city, so find yourself a dark site away from urban light pollution. A meteor shower is Mother Nature’s fireworks show. Don’t miss out.

3) Planetary Alignments. Because the planets all travel at different speeds around the Sun, they periodically catch up to one another. From our vantage point on Earth, the naked-eye planets can sometimes appear to be close to one another in the sky, as they pass. In addition, they may happen to be nicely placed near a crescent Moon, since the Moon is always changing position in our sky over the course of a month.

These picturesque groupings are called alignments, and the combination of bright objects makes an easy observing target even for city dwellers. Here are some nice upcoming alignments to watch for:

Looking west after sunset on July 31
Star maps created with Your Sky

On July 31, about a half hour after sunset, look west for a trio of bunched-up planets: Venus (the brightest), Mars (reddish-colored), and Saturn (golden-colored). Mercury is there too, but hanging low over the western horizon, so it will be a challenge.

Looking west after sunset on August 13

On August 13, about a half hour after sunset, look west for the aforementioned trio with the crescent Moon now joining them.

4) Milky Way. You might call this one the “main event,” as the Milky Way is our home galaxy. How wicked cool is it that we can look up at the night sky any time of the year and see an edge-on view of the spiral arms of our platter-shaped galaxy? Well, that is, if we get away from city lights. Unfortunately, 20 percent of the world’s population can’t see the Milky Way from where they live, due to light pollution.

Naked eye, we see what looks like a long filmy cloud stretching across the sky, but we know it’s composed of billions of distant stars. Yes, billions! If you haven’t experienced it, get yourself out to the country immediately if not sooner, and look up. You won’t be sorry.

Seeing Double

2010-04-15T23:02:00.017-06:00

I must disclose that, although I like a bright double star with a nice color combination as much as the next amateur, I don’t make a habit of observing doubles. I don’t own a double-star book or atlas. I don’t work my way through double-star checklists. And unless there’s enough separation to drive a Mack truck (or the starship Enterprise) between them, I don’t get particularly excited about the challenge of “splitting” doubles with my binoculars or telescope.

Oddly, my Mrs. Magoo eyes find it easier to discern structure in galaxies than to bring stars into sharp enough focus to reveal dim companions lurking nearby or to detect that One is really Two.

But I recognize that double stars have much to offer both beginning and seasoned observers, and that there are many avid and accomplished double-star hunters out there. One of these is Dee Friesen, a New Mexico amateur.

Dee is a Vietnam veteran and a retired commercial airline pilot. “Retired” being a relative term. Dee is very active with the local children’s science center and with public astronomy outreach in the area. He recently stepped down from a two-year stint as president of the local astronomy club. In addition, he teaches college-level astronomy and aviation. In his spare time, he and his wife travel extensively.

Dee sampling a local libation in New Zealand
Image by Ruth Friesen

I caught up with Dee recently to probe his fascination with double stars.

Whassup: So, Dee, why double stars?

Dee: I can barely make out “faint fuzzies” with the size telescope I have. I can’t discern very many features, so I’m not seeing much—other than, well, it’s there.

I like double stars because I like the theory of stars and the science of them. When I look at double stars, I can see color and magnitude. They tell me what they’re made of and what their temperature is, maybe even their relative size and distance. I feel close to what I’m seeing.

Whassup: How would you compare double stars to other targets?

Dee: From a practical standpoint, I can observe double stars on nights when the seeing and transparency aren’t good enough to see other things. I also find them easier to find. Plus, there’s beauty, there’s much more variation in color intensity, their separation, the comparative magnitude. You get interesting combinations.

I kind of enjoy not observing the obvious or popular things like the dim dark fuzzies. I like to be different!

Whassup: What else would you like us to know about doubles?

Dee: There was a time when double stars were looked at a lot. Go back 100 years, and they were looked at a lot by both professionals and amateurs.

I like observing double stars because I don’t need the biggest fanciest equipment, I can do it in many places, and I don’t have to have the best sky conditions to see them.

*****

Here are Dee’s picks for easy double stars for this time of year. If you want to give double stars a try, these are good targets for beginners. Happy hunting!

Polaris, the North Star, in the constellation Ursa Minor the Little Bear.
Telescope object. The position of the companion star rotates 15 degrees each hour, making it an excellent object to observe to detect the rotation of the Earth.

Mizar and Alcor, in the constellation Ursa Major the Big Bear.
Naked-eye object. The famous double in the handle of the Big Dipper. Also known as the Horse and Rider. Alcor is the dim companion to bright Mizar. If you can see both naked eye, you have good eyesight!

The Trapezium, in the constellation Orion the Hunter.
Telescope object. This is actually a quadruple star group in the Great Orion Nebula, the center “star” in Orion’s Sword. The four young stars, arranged in a diamond pattern, were born about a million years ago from the gas and dust in the nebula.

h3945, in the constellation Canis Major the Big Dog.
Telescope object. The stars are yellow and blue. Known as the "Winter Albireo" (after the famous blue & gold double star Albireo in Cygnus the Swan – summer object).

Algieba, in the constellation Leo the Lion.
Naked-eye object. An easy-to-find double in the Sickle asterism.

Tripping the Light Fantastic - Part 2

2010-04-01T23:55:00.008-06:00

Let’s continue our trip along the Winter Milky Way, this time exploring the northern end.

1) About an hour after your local sunset time, face north. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your left shoulder to the west, and you’ll be facing approximately north.

Star maps created with Your Sky

2) Moving up from the northern horizon, the first asterism (star pattern) you’ll spot is the House in the constellation Cepheus the King. It's a simple five-sided shape, not unlike a child’s drawing of a house. Its peaked roof is currently pointing straight up (toward the south).

3) Follow the westward curve of the Milky Way (toward the left) to find the Lazy W asterism of the constellation Cassiopeia the Queen. The W is standing on end, with the top of the W— the open end— facing right, or east.

4) Next in line on our glowing path is the asterism known as the Segment, in the constellation of Perseus the Hero. This is a curved line of six stars, oriented with its bulge protruding westward (to the left).

5) Continue a little farther along the Milky Way to finish up at the Pentagon asterism of the constellation Auriga the Charioteer. The very bright star that marks one of the Pentagon corners is the yellow-white Capella, sixth brightest star in Earth’s night sky.

6) With your head now tipped all the way back, can you spot where you left off last week when you swept up the Winter Milky Way from the southern horizon? The Milky Way is again bracketed by Taurus and Gemini, but this time Taurus the Bull is on the left (west) and Gemini the Twins are on the right (east).

Enjoy the spectacle of the Winter Milky Way through the warming spring, as it each night inches its way incrementally westward (or appears to, as the Earth continues eastward on its journey around the Sun). And don’t be sad when our friend WMW drops below the western horizon in June, because rising in the east to replace it will be another "light fantastic" we can trip together: the Summer Milky Way.

Tripping the Light Fantastic - Part 1

2010-03-25T23:03:00.006-06:00

After sunset on winter and early spring nights, you can spot the luminous band of the Winter Milky Way arching across the sky. The cloudlike apparition is the combined light of billions of stars in the spiral arms of our home galaxy. We look at these arms edgewise, from our position within the platter-shaped galaxy.

What we call the Winter Milky Way is the view looking outward, toward the edge of the galaxy. Contrast that with our summertime view of the Milky Way, when we look toward the center of the galaxy.

Let’s trip our way along the Winter Milky Way.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Star maps created with Your Sky

2) Moving up from the southern horizon, the first bright star you encounter is Sirius, brightest star in the constellation Canis Major the Big Dog and brightest star in the entire night sky. Extending southward from Sirius is the upside-down-Y asterism (star pattern) of the more prominent stars in Canis Major.

3) Follow the Milky Way up to the next recognizable pattern, the hourglass asterism of the constellation Orion the Hunter. This is a rectangle of stars cinched in the middle by a diagonal line of three evenly-spaced stars: Orion’s Belt.

4) Continuing upward, the Milky Way is next bracketed by Gemini the Twins on the left (east) and Taurus the Bull on the right (west). Gemini is made noticeable by its two brightest stars, Castor and Pollux, the names of the mythological twins. Taurus may be recognized by the V-shaped collection of stars known as the Hyades star cluster, the orange giant star Aldebaran, marking the Bull’s eye, and a spangled cloud above (northwest of) both star cluster and star: the famous Pleiades or Seven Sisters star cluster.

Next week, we’ll trip the light fantastic on the northern end of the Winter Milky Way.

Delusions of Grandeur

2010-03-11T23:22:00.017-07:00

I love that the naked-eye planets have unique colors. It's true that some beginning stargazers have actually accused me of being “delusional” when I’ve attempted to point out to them color differences among various planets and stars. And in the interest of full disclosure, I suppose I should mention that I’m pretty sensitive to the shades and subtleties of color, and am fully prepared to vigorously debate the relative merits of cornflower and periwinkle.

But three of the five naked-eye planets are visible in the night sky now, so you can put my claim to the test yourself.

Star maps created with Your Sky

Right after sunset, about one fist-width above the western horizon, look for the bright beacon of our neighboring planet Venus. (Never look directly at the Sun!) A fist-width is your fist held at arm’s length against the sky and measured across the knuckles. Venus is the third brightest celestial object in Earth’s sky, after the Sun and the Moon, and it blazes with a bluish-white hue.

About a half-hour after sunset, face east-southeast and look for bright planet Mars. It’s shining just below Castor and Pollux, the namesake stars of Gemini the Twins. You can also find it by drawing an imaginary line from Sirius, the brightest star in the sky, to Procyon, the bright star northeast of Sirius (that is, a little above it and to the left). Keep going past Procyon, a little less than the distance between Sirius and Procyon, and look for a reddish or orange-colored "star." It appears distinctively copper to me. This is the Red Planet, and its colorful name refers to the high concentration of iron oxide (aka rust) in the planet’s top layer of rock and dust.

About an hour after sunset, face east and look for a bright luminary coming up over the eastern horizon. It’s not quite as bright as Mars, but brighter than Regulus, the star at the bottom of the Sickle asterism (star pattern). The Sickle marks the head of the constellation Leo the Lion. The bright newcomer is the ringed planet Saturn, and it has a golden-yellow hue. This coloration is caused by sunlight (from our yellow Sun) reflecting off the ammonia clouds in Saturn’s upper atmosphere.

By the way, massive Jupiter and petite Mercury, the other two naked-eye planets, are aligned too close to the Sun right now— from our vantage point on Earth— to be visible. But yes, they too display unique hues.

That’s my story, and I’m sticking to it.

Deep-Sky Diving

2010-03-04T22:48:00.005-07:00

Spring is in the air. I can feel it in my bones. Unfortunately, that’s no longer a figure of speech, but a physical reality, as the arthritis that runs in my family now sends exploratory twinges through my joints whenever the weather changes.

I am, admittedly, something of a fair-weather observer. I rarely break out my telescope during December, January, or February. I don’t like the cold, never have, never will. During the winter months, I’m usually satisfied to do quick sessions of naked-eye stargazing, eliminating the need for long johns, clunky boots, and layering. Reconnecting with the familiar patterns of the winter sky—Orion’s hourglass, Canis Major’s upside-down “Y,” Auriga’s pentagon—and reassuring myself that they’re still there, just where I left them, proves to be as bracing as the cold slap of night air that accompanies our reunion.

It was an evening in March when I began my life as an amateur astronomer, when observing the sky became the context for my life. So March always feels to me like the start of stargazing season. And each time it rolls around, I can’t help but recall my first tentative forays into what I call “deep-sky diving.”

The comparison to scuba diving is no accident. When, as a beginner, I began attending star parties at my astronomy club’s private observatory, there was, on each occasion, a moment when I had to give up the daylight and surrender myself to the dark. I had to psych myself up each time to make that transition—to turn on my red flashlight and begin picking my way around the observing field equipped only with that dim, eerily-colored light. To be, in essence, completely out of my element.

Ironically, this fish-out-of-water feeling reminded me of the scuba diving vacation I took on the island of St. Croix, many moons ago. I had never been scuba diving and hadn’t had a single lesson (not even in a pool), but I had an irresistible desire to go. So I capriciously enrolled in a certification course down there, and off I went.

I was completely unprepared for the physical fear I would experience in letting go of my terrestrial, atmosphere-breathing self in order to immerse myself in a water-world. My first day in the ocean was spent in a series of exercises that each ended with my panicked bolt to the surface, where my exasperated instructor would berate me (as he should have) for doing something that was potentially hazardous to my health.

Then he had a breakthrough, and took me into shallow water (like a pool, perhaps?). He had me do exercises there until I became more comfortable with breathing underwater, moving me gradually into deeper water. Then I had my breakthrough, reaching that pivotal moment when my awe at the undersea world to which I had mysteriously gained access overtook my fear of relying on a regulator and tank for each breath.

By the end of the week, I was confidently doing 60-foot dives in open water and exploring dazzling, brilliantly-hued coral reefs.

And so it was to be a novice sky observer. The unfamiliar star patterns, the totally foreign equipment, the strange lingo, and the breadth of science knowledge those intense people-of-the-dark had—all were terribly intimidating. In that state of nervous excitement, making the transition from light to dark made me gasp for air like a panicky diving student. It wasn’t fear of the dark, but rather fear of the unknown, loss of control, and being out of my comfort zone that squeezed my chest those first few months.

Like breathing underwater, I got used to seeing in the dark. I learned which end of the telescope to look into, how to get the Moon into a telescope, how to identify naked-eye star patterns and find my way around the sky, what a glorious thing a globular cluster is, how to spot the pencil line of the Cassini Division in the rings of Saturn. It helped that I was on a mission, finally fulfilling a life-long interest and deeply-held desire. Pushing through the discomfort each time made me a little less uneasy for the next. Each new skill I acquired, each new term I learned, each new object I observed: each gave me a little bit more confidence and stoked my passion.

The first time I looked through a telescope, I was 43. I didn’t know what a star was, had no idea why the Moon looked the way it did as it went through its phases, couldn’t find the North Star. If you’re younger than 43 and are interested in getting started in hobby astronomy, don’t wait as long as I did. Do it now. The younger your eyes are, the more nuances you’re likely to see in celestial objects and the more years you’ll have to train your eyes to pick out those nuances.

If you’re older than 43, hop to it. Time’s a-wasting. There’s a lot to see out there in your universe. The more you find out, the more you’ll want to know, so you’d better get started. Trust me on this.

Whenever, however, wherever: embrace the dark. Oh, and don’t forget to breathe.

We Are Family

2010-02-11T21:54:00.012-07:00

I didn’t grow up with a sister (although I now have an awesome sister-in-law named Debbie). I guess that’s one of the reasons I find the Pleiades (PLEE-uh-deez) star cluster, aka the Seven Sisters, so intriguing. The idea of having six sisters is a difficult notion around which to wrap my imagination.

Right now, you can contemplate the Seven Sisters every evening, because about an hour after sunset when it’s good and dark, you’ll find them overhead, near the meridian.

They’re the sparkly little cloud of stars northwest (to the upper right) of the constellation Orion the Hunter. Lying between Orion and the Pleiades, you may notice a prominent, golden or pumpkin-colored star. This is Aldebaran (al-DEBB-uh-rahn), an orange giant that marks the eye of Taurus the Bull, the constellation within which the Seven Sisters reside.

Orion and Taurus, oriented with south at the bottom

Star maps created with Your Sky

The Pleiades are an open cluster, a group of stars that formed around the same time in the same nebula, or cloud of gas and dust. You may wish to think of an open cluster as a family group. There are several hundred members of this cluster, although you can see but a fraction with the naked eye.

Hobby astronomers use the Pleiades to test their visual acuity. Most people can pick out six separate stars when looking at the cluster naked-eye. Of course, amateurs try to push the envelope. The record for anyone of my acquaintance is 11 stars, seen at a very dark national park by a 20-something female astronomer. Yes, young eyes are a definite advantage; I’ve seen young adults easily pick out six or seven stars in light-polluted urban environments.

How many can you see? Test yourself at a dark location with no line-of-sight lights. To maximize your night vision, be sure to dark adapt first, that is, avoid all white light for a minimum of 20 minutes before attempting. To squeeze out every last star you can, also try averting your vision. In addition to looking directly at the cluster, try looking both slightly above and slightly below it. Sometimes additional stars will pop into view while using averted vision. This is because our peripheral vision is better than our straight-ahead vision.

Under a dark sky and with good observing conditions, you may notice a fuzziness or haziness associated with the Pleiades. No, you’re not imagining it. Not unlike car headlights moving through a patch of fog, the cluster is currently passing through an interstellar cloud of gas and dust called the Merope Nebula.

The Seven Sisters moniker by which most of the Western World knows the cluster refers to Greek legend: they’re the seven daughters of the giant Atlas (most famous for holding up the world) and the nymph Pleione (from whom the Pleiades get their name).

The named stars of the Pleiades
(oriented with south at the bottom)

Parents and daughters are immortalized in the names of the nine brightest stars in the cluster: Atlas and Pleione together to the east, and to the west, Alcyone (al-SIGH-oh-nee, the brightest star of the cluster), Merope (MERR-uh-pee, after which the nebula is named because it is densest near that star), Electra, Maia, Asterope, Taygeta, and Celaeno. The six that most people see naked-eye are Atlas, Alcyone, Merope, Electra, Maia, and Taygeta.

Known since antiquity, mentions of the Pleiades have been found in the written record as far back as several thousand years BCE. Nearly every ancient culture ascribed a mythological or folkloric identity to the celestial swarm. The Hindus saw a flame in the starry pattern--a symbol of their fire god. The Greek poets spoke of a flock of pigeons. In the French countryside, the cluster was known as the "Mosquito Net," a fact I’m sure you'll never see on a tourism brochure. The desert-dwelling Arabs imagined a herd of camels, and Hebrew writers memorialized a hen and her chickens. Natives of the Tonga Islands in the South Pacific named the object “Little Eyes.”

Many modern naked-eye observers of the Pleiades see the pattern of a little water dipper and mistakenly think they have found the much larger Little Dipper, the central asterism (star pattern) of the northern constellation Ursa Minor the Little Bear. Personally, I always see a little cluster of grapes. At recent public outreach events, people have told me they see items ranging from a lollipop to a microphone!

What do you see?

Unfortunately, my sister-in-law lives on the other side of the country, so I get to see the Pleiades more often than I get to see her. Sometimes, miles trump light years. But she’s often in my daily thoughts, and with the marvels of modern electronic communication, she’s always just an email away. As for those ladies of the night, my low-tech binoculars bring them— all seven— into sharp focus.

I’ve got all my sisters with me.

Chill Out

2010-01-28T21:19:00.006-07:00

Where are the coldest places in the universe?

The coldest temperature measured on Earth’s surface was at Vostok, Antarctica. In 1983, it reached minus 129 degrees Fahrenheit there.

The coldest place in our solar system is Neptune’s moon Triton, at minus 315 degrees Fahrenheit.

Two of the coldest known places in the universe are:
- intergalactic space, at an inhospitable minus 455 degrees Fahrenheit, and
- the Boomerang Nebula, a gas cloud being expelled by a dying star in our Milky Way Galaxy. At minus 457.6 degrees Fahrenheit, it’s currently the coldest known spot in the universe.

What’s the Ultimate Cold?

Absolute zero, the coldest theoretical temperature, is minus 459.67 degrees Fahrenheit. It has not yet been measured at any location, although scientists creating controlled environments in laboratories on Earth have come within a fraction of one degree.

That's Hot

2010-01-21T21:55:00.008-07:00

Where are the hottest places in the universe?

The hottest temperature measured on Earth’s surface was in the Lut Desert in Iran. In 2005, it reached 159 degrees Fahrenheit there.

The hottest place in our solar system is the center of our Sun, a sizzling 27 million degrees Fahrenheit.

Two of the hottest known places in the universe are:
- the cores of exploding stars called supernovas, at 100 billion degrees Fahrenheit, and
- inside gamma ray bursts— mysterious, energetic explosions originating from distant galaxies— estimated at a blistering 1 trillion degrees Fahrenheit.

What’s the Ultimate Hot?

The Big Bang, with an estimated temperature of 1-followed-by-32-zeros Kelvin, equivalent to 1.8-followed-by-32-zeros Fahrenheit.

Now that’s hot!

Where Does Space Begin?

2010-01-14T21:30:00.010-07:00

Space. We all know it’s the “final frontier.” But when you look up at the night sky from Planet Earth, where exactly does outer space begin?

To answer this question, we can first consider the dictionary definition of space: the region beyond Earth’s atmosphere. When you look up, you’re looking through many miles of the protective envelope of gases we call atmosphere. Earth’s atmosphere is composed primarily of elemental gases: more than 75% nitrogen, less than 25% oxygen, and about 1% argon. The remainder is an assortment of trace gases, as well as molecules such as carbon dioxide, ozone, and water.

Earth’s atmosphere is typically divided into five layers, and the demarcation of the layers is based upon whether temperature increases or decreases with altitude within the layer. The altitude ranges shown for the layers are approximate; they’re not precise or fixed measurements, because these altitudes can vary somewhat according to the season and the latitude of your location on Earth.

Looking up, your gaze crosses these layers, from lowest to highest:

#1 Troposphere - first 10 miles above sea level. Nearly all weather and clouds are found here, and most commercial aircraft fly in the upper troposphere. Although we stargazers normally revile clouds, this is a case where spotting one can orient you on your journey to outer space. Or simply look for the lights of a high-flying jet.

#2 Stratosphere - 10 to 30 miles. The stratosphere contains the important ozone layer, a protective band of specialized oxygen molecules that absorbs UV radiation from the Sun. The stratosphere is the upper limit of high-altitude weather balloons.

#3 Mesosphere - 30 to 50 miles. This is the layer where most meteors burn up, so look for a “shooting star” to locate the mesosphere. Strange clouds called noctilucent clouds,
and oddball types of lightning such as sprites and elves are also spotted in this layer.

#4 Thermosphere - 50 to 400 miles. The International Space Station (ISS) and the Hubble Space Telescope orbit high in the thermosphere. Consult this website to find out when you can watch the ISS pass overhead in your area; it’s very easy to spot since it’s so bright.

If you’re so lucky as to live far enough north to see the colorful spectacle of an aurora, aka the Northern Lights, you’re seeing solar particles colliding with atmospheric gases in the thermosphere.

#5 Exosphere - 400 to 800 miles. This layer is where stray atoms and molecules from Earth’s outer atmosphere escape into space. Hydrogen and helium, the two most common elements in the universe, are the main ingredients of the exosphere.

So, where does space begin? Unfortunately, there is no well-placed “Welcome to Outer Space” sign up there. The Earth’s atmosphere simply gets thinner and thinner (that is, less dense) with increasing altitude until it gradually merges with the cold expanse of space. However, since around the middle of the Twentieth Century, space has commonly been considered to begin at 62 miles (100 km) above sea level, just slightly into the thermosphere layer. This is where the atmosphere becomes too thin for aircraft to maintain altitude, in other words, where astronauts must replace aeronauts.

Can you see it? Somewhere between shooting stars and the Space Station, the final frontier begins.

Index of Posts 2007-2009

2010-01-07T03:58:00.012-07:00

Search this alphabetical index to find posts about specific constellations, planets, and other topics, indexed by the month and year they appeared. This index covers posts from 2007 through 2009. The majority of posts focus on stars (and other celestial objects) that you can see with the naked eye.

POST LOCATOR BY TOPIC

Andromeda Oct 2008
Andromeda Galaxy Dec 2009
Aquarius Oct 2009
Aries Nov 2008
Auriga Jan 2009
Bootes Oct 2008, Jun 2009
Burro Nebula Sep 2009
Camelopardalis Feb 2009
Cancer Apr 2008
Canis Major Feb 2008
Canis Minor Feb 2008
Capricornus Sep 2009, Oct 2009
Cassiopeia Dec 2007, Sep 2009
Cepheus Jan 2008
Cetus Dec 2009
Coma Berenices May 2009
Comets Nov 2007
Corona Australis Aug 2008
Corona Borealis Aug 2008
Corvus Jun 2009
Delphinus Oct 2008
Draco Jun 2009
Equilux Mar 2008
Equinox Mar 2008
Equuleus Oct 2009
Eridanus Jan 2009
Galileo Jan 2008, Jan 2009
Gemini Dec 2007, Feb 2009
Hercules Sep 2008
Jupiter Jul 2008
Lacerta Dec 2008
Lepus Feb 2008
Libra Jul 2009
Mercury May 2008
Meteors Dec 2007, Aug 2008, Apr 2009
Milky Way Dec 2008
Moon Nov 2007, Mar 2008, Apr 2008, May 2008, Jun 2008, Jul 2008, Sep 2008, Nov 2008, Dec 2008, Jul, 2009, Nov 2009, Dec 2009
Movies May 2008
Music Aug 2008
Ophiuchus July 2009, Aug 2009
Orion Jan 2008, Feb 2008
Pegasus Dec 2007
Perseus Mar 2009
Pisces Nov 2009
Piscis Australis Nov 2009
Puppis Feb 2009
Sagittarius Aug 2009
Satellites Oct 2008
Saturn Dec 2008, Apr 2009
Scorpius Jul 2008
Serpens Jul 2009
Solstice Dec 2007
Summer Triangle Oct 2008
Taurus Jan 2008
Telescopes Nov 2007, Jan 2008
Triangulum Jan 2009
Ursa Major Jun 2008, May 2009
Ursa Minor Jun 2008
Venus Jan 2008, Feb 2009, Mar 2009
Virgo Apr 2009
Websites Mar 2009
Whirlpool Galaxy May 2008
Winter Hexagon Mar 2008
Zodiacal Light Mar 2008

Once in a Blue Moon

2009-12-31T23:06:00.011-07:00

Four hundred years ago, in Galileo’s time, a once-in-a-blue-moon event would occur, well, never, as the phrase referred to something so absurd as to be nonexistent. It would occur with the same frequency as, for example, hell freezing over.

In the 20th century, the expression came to mean a very rare event that, nonetheless, could actually happen. Astronomically speaking, Blue Moon came to refer to the second Full Moon in a calendar month, which typically occurs every two and a half years.

The Full Moon, with a few drops of artificial color

Tonight, on New Year’s Eve, as we leave behind the “oughts” of our brave new century and enter the “tens,” we can enjoy a view of a Blue Moon: the second Full Moon this month and the first Blue Moon to occur on New Year’s Eve since the close of 1990, nearly twenty years ago. Tonight the brilliant Moon waxes poetic, in what seems a perfect close to 2009, the International Year of Astronomy.

*****

Once in a blue moon, those of us who evangelize for astronomy get an opportunity to wear our hearts on our sleeves and have it fully sanctioned by such august bodies as the International Astronomical Union and the United Nations. The International Year of Astronomy, the quadricentennial of Galileo’s achievement, was certainly such an opportunity--if you seized it.

As I take stock of this past year, I feel gratitude for having been able to participate in communicating astronomy to the public during IYA--for having had the time, the resources, and the invaluable support of others in order to do so. It was an unforgettable adventure.

With a little help from my friends, I co-instructed weekend workshops in astronomy at a National Wildlife Refuge; gave slide show presentations at libraries; taught astronomy to gun-slinging women at an NRA facility; gave people views through my telescope at museums and public spaces; co-organized a free public astronomy event for girls; conceptualized a nonprofit science education organization which will launch next year; and began writing a second astronomy-related book (because working on one wasn’t challenging enough?!) I indulged myself in paying my passion forward, for whatever it may be worth.

Thank you to all who patronize my blog, especially those gracious individuals who leave comments. Thank you to my fellow astronomy enthusiasts who generously offered topic suggestions for this year’s “Astronomy Essentials” feature: Aileen O’Catherine, Barry Spletzer, Bob Havlen, David Nelson Blair, and Linda Hixon.

And thank you to everyone who this year said to me, “This is the first time I’ve looked through a telescope!” or “I never understood before what the Moon’s phases were!” or “Wow, look at those craters!”

Once in a blue moon, your heart is full.

Astronomy Essential: The Moon is visible during the day, nearly every day.

We tend to think of the Moon as a nighttime object, probably because its brightness is amplified against the dark backdrop of the night sky.

But, if you remember to look for it, you can find the Moon in the daytime sky. It’s visible with the naked eye for part of each day, nearly every day. The only times during its month-long cycle that the Moon doesn’t grace the daytime sky are: 1) Full Moon, when the Moon rises at sunset and sets at sunrise, and 2) a day or two surrounding New Moon, when it’s too close to the Sun in the daytime sky and is masked by the Sun’s glare. (Never ever look directly at the Sun!)

We see the Moon during the day both because it is so bright and close, and because it is in orbit around us and its “window of visibility” is always shifting relative to Earth’s day/night cycle.

Island Universe

2009-12-24T22:18:00.009-07:00

Four hundred years ago, in 1609, the Italian astronomer Galileo Galilei turned his homemade telescope skyward and began a series of astronomical observations that would redefine human horizons. Among his discoveries was the realization that the Milky Way is a horde of stars too numerous and faint to be resolved with the naked eye. Before that telescopic revelation, the nature of the Milky Way--the name given to the hazy band of light stretching across the sky--was not known.

Over a century later, the German philosopher Immanuel Kant postulated that the Milky Way was a vast, disk-shaped collection of stars. He further suggested that the faint, fuzzy celestial clouds seen through telescopes and known as “nebulas” were large, distant collections of stars similar to the Milky Way. He called these nebulas island universes.

Although proof of the distance and separate nature of these island universes would not be acquired until Edwin Hubble’s work in the 1920s, Kant was correct. We merely had to wait another 150-plus years for our horizons to be again redefined: to learn that the Milky Way, our home galaxy, was not home to many of the so-called nebulas. The Milky Way was not the whole enchilada. There were other galaxies, other island universes, out there.

*****

When you look at the sky on a clear night from a dark location, at any given time you can see about 2500 stars with the naked eye. A telescope can reveal millions more. Regardless of whether you’re observing with the naked eye or the aided eye, every star you can see is in the Milky Way Galaxy. Essentially, you look out at the cosmos through the vast starfield of your home galaxy, your own island universe.

But you can also see beyond. In fact, there’s an island universe visible to the naked eye, if you observe from a dark site. Originally called the Great Andromeda Nebula, Hubble’s work confirmed its galactic nature, and it became known as the Andromeda Galaxy. At an estimated 2.5 million light years away, it is the most distant object that the average person can see naked-eye. It is the nearest spiral galaxy to the Milky Way, and it’s comparable to our home galaxy in size and mass. Looking at the Andromeda Galaxy is a bit like looking in the mirror, that is, on a galactic scale.

Andromeda Galaxy

Looking south to the Great Square and the Chains of Andromeda
Star maps created with Your Sky

2) First, locate the Great Square asterism (star pattern) in Pegasus, high in the southern sky, on or near the meridian.

3) Next, find the Chains of Andromeda, the two strands of stars that arc upward and to the left of the star that marks the Square’s upper left corner. Now look above the middle star of the upper chain for a faint, fuzzy patch. A Persian astronomer of the 10th century called it the “little cloud,” an apt description.

If you can’t see it, you may need to try again at a darker site with less light pollution. Additionally, your sky transparency, or atmospheric clarity, can be negatively impacted by the presence of clouds, haze, dust, or humidity. This could impact your ability to see a faint object like the Andromeda Galaxy. If this is the case, you should try again when conditions are improved.

It’s worth a little extra effort for the thrill of seeing, with your own eyes, a world beyond your galactic neighborhood: an island universe where perhaps other curious skywatchers are turning their eyes toward you, and wondering.

Astronomy Essential: The universe has a dark side.

By studying gravity’s influence on the gas that exists between galaxies in galaxy clusters--gas that can only be seen in X-ray wavelengths of light--astronomers can determine how much matter there is in the cluster. Interestingly, these measurements show that there is far more mass present than can be accounted for by the ordinary matter in the cluster.

From these results, astronomers have deduced the presence of another type of matter that can’t be observed directly (at least not yet). They call this dark matter.

Discoveries in the 1990s that the expansion of the universe is speeding up and in 2003 that the universe is flat suggest to astronomers the presence of yet another substance in the universe, in the form of energy. They call this dark energy. Like dark matter, dark energy is not directly observable, but dark energy would account for the density needed to maintain both a flat universe and a universe whose expansion is accelerating.

Current estimates for the structure of the cosmos indicate that the ordinary matter with which we‘re familiar--matter made of atoms, such as trees, rocks, people, air, planets, and stars--constitutes less than 5% of the universe! The rest is mysterious, unseen dark matter and dark energy. Understanding their nature is one of the key areas of exploration in astronomy today.

Whale's Tail

2009-12-10T20:48:00.012-07:00

Note: There will be no December 17 post. Enjoy this post or browse my older posts. I'll be back with a new post on December 24.

The brightest star in the autumn constellation Cetus the Whale is known by two traditional names: Deneb Kaitos (DENN-ebb KYE-tohs) and Diphda (DIFF-duh). The former is Arabic for whale’s tail, as the star marks the position of the celestial sea creature’s tail. The latter is more commonly used by amateur observers, and it’s from an Arabic phrase meaning second frog. The “first frog” is the nearby--and noticeably brighter--star Fomalhaut in Piscis Australis the Southern Fish.

Thar she blows!

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Looking south to the Great Square and Cetus
Star maps created with Your Sky

2) First, locate the Great Square asterism (star pattern) in Pegasus, high in the southern sky, on or near the meridian.

3) Now, let’s starhop. Using the two easternmost stars in the Square as pointers, draw an imaginary line between them and extend it towards the southern horizon. Traveling a little more than twice the distance between the two pointer stars, you’ll come to the bright star Diphda.

Can you discern a golden hue in the star’s light? Diphda is an orange giant star, nearly 150 times as luminous as our Sun. Of course, from our perspective nearly 100 light years away, it’s just another twinkle light in the autumn night sky. After all, one light year is nearly six trillion miles! So we can be forgiven if we think our Sun has more star power.

4) Reacquaint yourself with the “first frog,” Fomalhaut, to compare it to Diphda in color and brightness. Use the two westernmost stars in the Great Square as pointers this time. Draw an imaginary line between them and extend it towards the southern horizon. Traveling a little more than three times the distance between the two pointer stars, you’ll come to bright Fomalhaut, which will be closer to the southern horizon than Diphda.

Since Fomalhaut is a white star, try comparing the two, which may enhance Diphda’s subtle golden color. Fomalhaut’s brightness as seen from Earth, also known as apparent magnitude, is about two and a half times greater than Diphda’s, so you should discern a difference.

Astronomy Essential: The Milky Way is a barred spiral galaxy.

Our home galaxy was first determined to be a pinwheel-shaped spiral galaxy by radio astronomers in the 1950s, who began the on-going process of creating detailed maps of our galaxy’s structure. The curved “arms” of spiral galaxies--which radiate out from a dense galactic core--are regions of active star formation, which is why they are detectable in a variety of wavelengths and able to be mapped.

In 2005, new surveys of the galaxy in infrared light--conducted with the Spitzer Space Telescope--revealed a dense, bar-like congregation of stars cutting across the galaxy’s center. Extraterrestrial observers in other galaxies, positioned so as to have a face-on telescopic view of the Milky Way, would immediately recognize it as a barred spiral type.

Gibbous Moon

2009-11-26T23:22:00.009-07:00

Note: There will be no December 3 post. Enjoy the November 26 post or browse my older posts. I'll be back with a new post on December 10.

The night sky is dominated right now by a waxing gibbous Moon, that is, a Moon that is more than half illuminated and that is growing in percent illuminated. Put another way, it is the phase of the Moon that occurs between First Quarter (also known as “Half Moon”) and Full Moon.

Once Full Moon occurs, our nearest celestial neighbor will enter its waning gibbous phase, when it is more than half illuminated and shrinking in percent illuminated. In other words, the waning gibbous Moon is the phase that occurs between Full Moon and Last Quarter (the other “Half Moon” phase).

If you’re curious about the etymology of these terms, as I was, you’ll find the following of interest.

“Wax” means to increase in size or intensity, and comes from the Old English weaxan, meaning to increase. “Wane” means to diminish in size or intensity, and comes down to us from the Old English wan, meaning deficient, and the Latin vanus, meaning empty. Finally, “gibbous” means marked by swelling, or humpbacked, and comes from the Latin gibbus, meaning hump.

Phases of the Moon
Credit: http://starchild.gsfc.nasa.gov/

So if the Moon appears humpbacked, it is gibbous. If the western--or right--side of the humpbacked Moon is illuminated, it’s waxing gibbous. If the eastern--or left--side of the swollen Moon is illuminated, it’s waning gibbous.

And if the slithy toves gyre and gimble in the wabe, it's plain gibberish.

Astronomy Essential: Stars do not twinkle.

Stars sometimes appear to blink on and off rapidly, dim and brighten wildly, and scintillate in a variety of colors. This “twinkling” is merely an optical distortion caused by the turbulence of Earth’s atmosphere, through which starlight must travel to reach our eyes. The starlight is “bent” in many random directions as it travels through atmospheric layers and pockets of different density and temperature. Our eyes interpret this bending or refraction of the light as twinkling.

This effect is usually most pronounced near the horizon, because the light from a star near the horizon must travel a longer path through the atmosphere to reach our position than it would if the star were positioned directly above us.

The next time you notice stars near the horizon twinkling, check the stars directly above you to see if they are in fact twinkling less or not twinkling at all.

Tropical Fish

2009-11-19T22:19:00.011-07:00

There’s a third fish in the autumn sky, less heralded than the Pisces duo and--in the Northern Hemisphere--best seen from warmer latitudes such as the southern U.S. and Mexico. Considered a Southern Hemisphere constellation, this tropical creature is Piscis Austrinus the Southern Fish.

One would have to travel well south of the equator to, say, Santiago, Chile or Sydney, Australia in order to see Piscis Austrinus at the zenith, directly overhead. However, many northerners with a clear view of the southern horizon should be able to locate it easily because its brightest star is among the top twenty brightest stars in the night sky. Folks in far northern latitudes, such as Fargo, North Dakota, will have a bit more of a challenge because the star sits only about a fist-width above the southern horizon. A fist-width is the width of your fist, held at arm’s length against the sky, and measured across the knuckles.

Piscis Austrinus (PIE-siss aw-STRY-nuss) swims solo, south of Aquarius. In fact, the stream of water from the Water Bearer’s Water Jar has traditionally been depicted as pouring into the open mouth of Piscis Austrinus.

Piscis Austrinus (under Aquarius) in John Flamsteed’s 1729 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

I’m ready for a dip in warm, tropical waters. How about you?

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Looking south to Fomalhaut in Piscis Austrinus
Star maps created with Your Sky

2) Look south to find the Southern Fish, floating just east of the meridian. You can use the Bandanna of Capricornus to locate it, especially this year while the Bandanna is occupied by brilliant Jupiter. Jupiter is the brightest “star” you’ll see in the southern sky and the first celestial landmark to become visible after sunset.

3) The luminary you’re looking for is the only bright star in the Northern Fish and the only one with a traditional name: Fomalhaut. Fomalhaut (FOAM-uh-lott) is from the Arabic for mouth of the fish, and it marks the gaping maw of the oddly thirsty fish.

Only 25 light years away, this seemingly ordinary white star is surrounded by an emerging solar system four times the diameter of ours. A planet several times larger than Jupiter has been imaged in orbit around Fomalhaut.

It’s difficult to mistake Fomalhaut for any other star, since there are no other bright stars near it. In fact, Fomalhaut has been characterized by a number of writers as “lonely.” Once you spot it and take in the oceanic expanse of dark sky and dim stars around it, you’ll understand why its alternate classical name was Piscis Solitarius--the Solitary Fish.

Astronomy Essential: The zodiac is the band of 12 constellations that lie along the ecliptic.

The ecliptic is the imaginary line that represents the path the Sun appears to take across the sky, as seen from Earth. Because the Earth, the Moon, and the planets all lie in roughly the same plane as they orbit the Sun, the ecliptic can also be said to represent the plane of the solar system. This is why the Sun, Moon, and planets all appear to move along the ecliptic and through the constellations of the zodiac.

Although conventionally we say the Sun, Moon, and planets move “through” the zodiac, we need to remember that the stars of the zodiacal constellations are much farther away than the Sun, Moon, and planets. In essence, they form the backdrop for those solar system bodies.

The constellations of the zodiac are: Aries the Ram, Taurus the Bull, Gemini the Twins, Cancer the Crab, Leo the Lion, Virgo the Maiden, Libra the Scales, Scorpius the Scorpion, Sagittarius the Archer, Capricornus the Sea Goat, Aquarius the Water Bearer, and Pisces the Fishes.

The Ties That Bind

2009-11-12T21:11:00.009-07:00

Last week, we located the most recognizable asterism (star pattern) in the constellation Pisces the Fishes: the Circlet. The Circlet marks the body of the Western Fish, the fish that points westward.

The other fish in the Pisces (PIE-seez) pair is the Northern Fish, the fish that points northward. Starting at the Circlet, let’s see if we can reel in the other fish on our line.

The Northern Fish (left) and the Western Fish (right) of Pisces
Courtesy of Linda Hall Library of Science, Engineering and Technology

2) First, locate the Circlet. If you need help, consult last week’s post.

Looking south to Pisces

Star map created with Your Sky

3) Heading east from the Circlet is a streamer of eight naked-eye stars. This is the string binding the Western Fish. The terminal star--and the brightest in the string-- is called Alrescha. Alrescha (ahl-RESH-uh) is Arabic for the cord. It is also known as the Knot Star, because it marks the knot that binds the two strings--and the two fishes--together.

Alrescha is a binary star, that is, a system of two stars in orbit around each other. In Alrescha’s case, both are white dwarf stars. Because of their close proximity from our vantage point, we see their combined light as one star.

4) Heading northwest from Alrescha is the binding cord for the Northern Fish. From Alrescha, look for two bright stars spaced an equal distance apart. The second one, and the brighter of the two, is Kullat Nunu. It’s a little brighter than Alrescha. Kullat Nunu is Babylonian for cord of the fish. It’s a yellow giant and the brightest star in Pisces.

Beyond Kullat Nunu, the Northern Fish disintegrates into a jumble of not very bright stars with no readily apparent pattern to pick out. Suffice it to say that the ancients imagined a second succulent fish tethered there, ready for the fire.

Pass the tartar sauce, please.

Astronomy Essential: There are stars in the daytime sky.

If you could turn off the Sun during daylight hours--like you would turn off a light bulb--you would see a star-filled sky appear.

As the Earth spins, we are always looking out at the Milky Way and its legions of stars. During the day, those stars form a backdrop to the Sun. Consequently, they are--for the most part--not visible due to the Sun’s glaring brightness.

Ambitious amateur astronomers challenge themselves by trying to spot the brighter stars during the day, using a telescope as well as precise coordinates so they know where to point it. Popular daytime targets include: Castor and Pollux, the Gemini Twins; Rigel and Betelgeuse, brightest stars in Orion; Sirius, brightest star in our sky (after the Sun); and even not-so-bright Polaris, the North Star.

Circling the Circlet

2009-11-05T23:22:00.012-07:00

Like Aquarius, Pisces the Fishes is another faint constellation that’s a little difficult to spot. But if you can find the Great Square of Pegasus, you can locate an asterism (recognizable star pattern) in Pisces and thereby orient yourself to the fishy constellation.

On classical star atlas maps, Pisces is typically represented as two fishes, each tied with a string at the tail, and the two strings joined with a knot. One fish heads west, and the other fish heads north.

Pisces is a constellation of the zodiac. The zodiac is a band of twelve constellations that straddles the ecliptic. The ecliptic is the imaginary line that represents the path the Sun appears to take across the sky, as seen from Earth. Because the Earth, the Moon, and the planets all lie in roughly the same plane as they orbit the Sun, the ecliptic can also be said to represent the plane of the solar system. This is why the Sun, Moon, and planets all appear to move along the ecliptic and through the constellations of the zodiac.

Pisces in Johann Bode’s 1782 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

Let’s circle our quarry.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Looking south to the Circlet
Star maps created with Your Sky

2) First, locate the Great Square asterism in Pegasus, high in the southeastern sky.

3) Now look under the Great Square for a circular arrangement of five naked-eye stars. If you don’t see it, you’ll need to try again at a darker site, away from urban and suburban light pollution. This is the Circlet asterism, the most recognizable star pattern in Pisces. It lies a little east of the Water Jar asterism in Aquarius. The Circlet marks the body of what is known as the Western Fish, the fish that points westward.

The Circlet of Pisces

4) The stars in the Circlet do not have traditional names, but just west of the Circlet is Fum al Samakah, which is Arabic for fish’s mouth, and which marks the gaping mouth of the Western Fish. Fum al Samakah is a blue-white dwarf star, nearly 500 light years away (one light year is nearly six trillion miles).

Next time, we’ll locate the Northern Fish. Then you’re all invited to the fish fry.

Astronomy Essential: There are planets around other stars.

Thus far, astronomers have discovered over 350 planets orbiting stars other than our Sun. These are known as exoplanets. It seems the familiar eight planets of our solar system are not unique in the universe.

Astronomers use a number of methods to detect the presence of planets around distant stars. Orbiting planets can make stars wobble a bit, and that wobble can be measured to confirm the existence of a planet that can’t be directly observed. The periodic dimming of a star when an orbiting planet passes in front of it--that is, transits it from our perspective on Earth--can be measured. And in rare cases, exoplanets can be directly imaged.

The exoplanets found thus far are primarily gas giants and ice giants. The holy grail of current exoplanet detection research is to find terrestrial planets--rocky planets like Earth--orbiting in the habitable zone of their suns where, potentially, liquid water and life might exist.

The Water Jar

2009-10-29T23:08:00.011-06:00

Between the Great Square of Pegasus and the Bandanna of Capricornus lies the rather nondescript constellation of Aquarius the Water Bearer.

Aquarius was traditionally depicted as a man upending an urn and pouring water into the mouth of a fish. A bizarre, inscrutable image, perhaps, but nevertheless, the way the ancients imagined it.

Saving the Aquarius constellation from obscurity are two bright stars and a little asterism (recognizable star pattern). Let’s see if we can spot them.

Aquarius in Johann Bode’s 1801 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

Looking south to Aquarius the Water Bearer
Star maps created with Your Sky

2) First, locate the Great Square asterism in Pegasus, high in the sky, just east of the meridian, and the Bandanna asterism of Capricornus, low in the sky, just west of the meridian.

3) Now look between the Great Square and the Bandanna for two bright stars, Sadalsuud and Sadalmelik. Sadalsuud (sah-dull-suh-OOD), from the Arabic for the luckiest of all, is the brightest star in Aquarius. Sadalmelik (sah-dull-MELL-ick), from the Arabic for the luck of the king, is the number two Aquarian. Both stars are yellow supergiants, which is a relatively rare star type.

Don’t confuse them with nearby Enif, the nose of the winged horse Pegusus. Enif is a little brighter than the best and brightest of Aquarius.

4) Just east of Sadalmelik is a little “Y” of four fainter stars. This is the Water Jar asterism, which marks the position of the upended urn in the ancient star picture. If you can’t spot all four, you’ll need to try again at a darker site.

The Water Jar asterism of Aquarius

Of the four stars, only one has a traditional name: Sadachbia. Sadachbia (sah-DUCK-bee-yah), from the Arabic for luck of the tents, is a white star. We call the other three stars Eta, Zeta, and Pi, for their star catalog designations. Zeta, in the center, is the brightest star in the asterism.

Although Sadachbia is not the brightest of the Water Jar quartet, it clearly had enough significance to the ancients to be named and to be considered lucky like Sadalsuud and Sadalmelik. Perhaps whenever the early Arabs thanked their lucky stars, they had Aquarius in mind.

Astronomy Essential: We don’t see celestial objects the way cameras do.

Beginning stargazers are sometimes disappointed by their first telescopic view of a deep-sky object such as a galaxy, nebula, or star cluster. They expect the technicolor, high-resolution panoramas seen in Hubble Space Telescope images, which have become part of our public consciousness.

Instead they get small, fuzzy, black-and-white blobs.

What technology-savvy newcomers don’t realize is that human eyes are limited instruments. Collecting and integrating the faint light from distant objects— light that has traveled many trillions of miles to reach us— pushes our eyes to the limits of their ability. And in low-light situations, we don’t see color well. Compare that to the ability of an ultra-sensitive camera chip to detect extraordinarily faint light and integrate it over a long exposure time. Add to that the ability of specialized image-processing computer software to “stack” multiple images of an object, as well as color-correct the composite to approximate the color signatures of the chemical elements found in each celestial object.

What we can’t accomplish at the telescope eyepiece, we can accomplish at the computer keyboard.

At the end of the day, however, there is no substitute for looking at an astronomical object with your own eyes, collecting on your retinas those faint photons of light that have traveled many years to reach you, and discerning an image of a far-away world in real time, live, under your own power.

The Little Horse Head

2009-10-22T22:41:00.020-06:00

Tucked between Pegasus the Winged Horse and Delphinus the Dolphin is the second smallest constellation in the sky: Equuleus the Foal. Equuleus (ee-KWOO-lee-yuss) is in fact the smallest constellation that can be seen from most latitudes in the Northern Hemisphere.

Like neighboring Pegasus, Equuleus is not a whole horse. Although the entire front half of Pegasus— head, front legs, torso, and wings— soars overhead, poor Equuleus must make do with a disembodied head. Make that an inverted disembodied head. Like Pegasus, Equuleus is upside down in the sky.

First mentioned by the Egyptian astronomer Ptolemy in the second century CE, the origin of the little horse head in the sky is unknown.

Pegasus, Equuleus, and Delphinus in J. Middleton’s 1842 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

You won’t need a carrot or a sugar cube to coax the stellar foal into view. You will, however, need a dark-sky location and you’ll need to be dark adapted, because his stars are not terribly bright.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Looking south to Equuleus the Foal
Star maps created with Your Sky

2) First locate the Great Square of Pegasus asterism (star pattern) high in the southeast, and jutting out from it to the west, the right angle asterism that represents the neck and head of Pegasus. The star at the end of the right angle is Enif (EE-niff) which is from the Arabic for nose. Enif marks the snout of Pegasus.

3) Next locate the Dolphin asterism, the prominent star pattern in the little constellation of Delphinus the Dolphin (dell-FINE-uss). The head of Pegasus, punctuated by Enif, points to the Dolphin, which is currently on or near the meridian about an hour after sunset.

4) Now that you have your two celestial landmarks identified, look midway between Enif and the Dolphin— and then slightly south— to locate the four-star quadrilateral asterism that comprises the brightest stars in Equuleus. This asterism is known as the Horse’s Head.

5) The brightest of the four stars is Kitalpha (kitt-AL-fuh), from the Arabic for section of the horse. Kitalpha is a binary star, that is, a system of two stars in orbit around each other. In Kitalpha’s case, the two stars are a yellow giant and a white dwarf. Because of their close proximity from our vantage point, we see their combined light as one star. These two are so close, you won’t even be able to split them in a telescope.

6) The other three stars have no traditional name, so we call them (moving clockwise around the quadrilateral from Kitalpha) Beta, Delta, and Gamma for their star catalog designations. Delta is interesting in that it is also a binary star, with its two components a yellow-white dwarf and a yellow dwarf, the latter quite like our Sun. If you have a telescope, try splitting the two components.

Delta and Gamma mark the snout of the upside-down foal‘s head. He surely must be related to Pegasus. He’s a chip off the old block.

Astronomy Essential: The universe is 13 billion years old.

Currently the best estimate as to the age of our universe is 13 billion years (and change). In other words, 13 billion years have elapsed since the Big Bang.

Astronomers calculate this primarily by: 1) determining the age of the oldest stars, and 2) measuring the rate at which the universe is expanding and then extrapolating that back to the compressed state of the Big Bang.

In turn, identifying and dating the oldest stars is dependent upon what astronomers’ have learned thus far about star mass and about the life cycles of stars.

Measuring the universe’s rate of expansion is dependent upon astronomers’ knowledge of the current density and composition of the universe. In addition, they can peer back in time by observing and mapping the cosmic microwave background radiation, the afterglow of the Big Bang and the oldest light in the universe.

Get Out Your Bandannas

2009-10-08T21:08:00.014-06:00

Note: There will be no October 15 post. Enjoy the October 8 post or browse my older posts. I'll be back with a new post on October 22.

Let’s wrap up our exploration of Capricornus the Sea Goat with a telescopic look at one of my favorite deep-sky objects: the globular cluster Messier 30.

Globular clusters, or “globs” as they are called in the astronomy community, are dense balls of gravitationally bound stars. There are at least 150 known globs scattered about our home galaxy, the Milky Way. Globs contain tens of thousands to millions of stars.

A number of the brighter globs that can be spotted from the Northern Hemisphere are found in the Messier catalog (MESS-ee-yay). This is the catalog of 110 deep-sky objects compiled by the famed 18th century French astronomer Charles Messier, who observed from the rooftops of Paris. The Messier catalog contains some of the finest binocular and telescope objects in the night sky and is widely used by amateur astronomers as an observing list.

Globs are my favorite type of deep-sky object, and Messier 30— or M30 as it is commonly known— is one of my favorites because of its irregular shape. I find the globs that are a bit asymmetric, rather than perfectly spherical, to have the most visual appeal.

Use the star map below to locate M30, just to the left (east) of the Bandanna asterism. If you have a dark sky (Moon-free and light pollution-free), try spotting it with binoculars first. If successful, you’ll see a small fuzzy ball, something like the end of a Q-tip.

Messier 30 in Capricornus
Star maps created with Your Sky

But honestly, M30 is one of those objects that is best examined in a telescope. Depending on your aperture (diameter of the primary optical element)— which dictates your telescope’s ability to collect light from faint celestial objects— you may begin to resolve the cluster. If so, the stars in the cluster will begin to separate into distinct points of light, and you’ll be able to truly appreciate M30’s endearing quirkiness.

Once you’ve located M30 with a low-power eyepiece (high mm number), switch to a high-power eyepiece (low mm number) and pump up the volume. This object warrants the most magnification you can muster.

Globular cluster M30
Source: NASA/ESA

Honk if you love globs. Or just wave your bandanna.

Astronomy Essential: Human eyes can adapt to the dark.

Seasoned night-sky observers typically go through a ritual called dark adaptation prior to embarking on an evening of stargazing. Dark adapting involves avoiding all white-light sources for 20 to 30 minutes, which prepares their eyes for enhanced seeing in the dark.

In a dark environment, first the human eye responds with pupil dilation. Next, chemical changes occur in our retinas’ receptors: the rods and cones. The rods become super-sensitized to light, thereby enabling us to see in low-light conditions.

As you can imagine, dark adapting— and then avoiding bright light once adapted— results in greater success seeing faint celestial objects through binoculars or telescopes, as well as with the naked eye. Astronomers maintain their dark adaptation by using red-light flashlights, since red light does not interfere with night vision.

The Sea Goat Revisited

2009-10-01T22:11:00.009-06:00

In my previous post I introduced you to Capricornus the Sea Goat and its defining asterism (star pattern), the Bandanna.

This time, let’s take a look at the more prominent stars of the Bandanna— the ones with traditional names. They all lie along the top of the Bandanna. If you need help locating Capricornus, review my previous post.

The top left corner of the Bandanna is marked by Deneb Algedi, from the Arabic for tail of the goat. Deneb Algedi (DENN-ebb uhl-JEDD-ee), the brightest star in Capricornus, is a white star that lies about 39 light years away. A light year is the distance light travels in one Earth year, nearly six trillion miles.

The Bandanna of Capricornus
Star maps created with Your Sky

Moving right (or west), the next bright star is Nashira (nah-SHEE-rah). Its precise meaning in Arabic is unclear, but it references “luck.” Nashira is also a white star, but it lies nearly 100 light years farther away than Deneb Algedi.

Traveling across the top of the Bandanna toward the upper right corner, we next come to Dabih. Dabih (DAH-bee) is from the Arabic for luck of the slaughterer, a reference to the seasonal sacrifice made by Arabs when Dabih first appeared in the dawn sky before sunrise. Dabih is a binary system, that is, two stars in orbit around one another. The brighter of the pair is an orange giant, and the companion star is a blue-white giant. You should be able to “split” Dabih, that is, separate the two component stars, using binoculars.

The upper right corner of the Bandanna is marked by Algedi, Arabic for goat. Algedi is also two stars, but unlike Dabih, the two components are not gravitationally associated. They simply appear close together by line of sight from Earth. This type of double star is called an optical double. Coincidentally, both components of Algedi are yellow stars, similar in temperature to our Sun.

If you have keen eyesight, you should be able to split Algedi with the naked eye. If this proves difficult, the magnification provided by a pair of binoculars will bring you certain success.

Astronomy Essential: Constellations are three-dimensional.

We experience the night sky as if it’s an upside-down bowl, painted black, with an artistic sprinkle of luminous white dots. In other words, we experience it as a two-dimensional plane.

The connect-the-dot star pictures of the ancients, persisting across the centuries, do nothing to disabuse us of this notion.

We stargazers must, therefore, make a conscious effort to remember that the constellations and asterisms we use to navigate the sky are three-dimensional. Although we perceive a particular star pattern in two dimensions, the stars of that pattern are distributed in three dimensions. Some of the stars are relatively close to us, and some are relatively far from us.

If we could fly out into space and “through” a particular constellation, we would experience this first-hand. Zipping past each star in turn, we would finally see the third dimension— the depth— of space. We would finally understand that constellations and asterisms and any other patterns our brain seeks to make from random star positions are simply the artificial constructs of Earth-bound life forms with active imaginations.

The Sea Goat

2009-09-24T22:46:00.019-06:00

Last night the cats fought over who would sleep under the blankets against human warmth and in the sheepskin-lined cat bed. It was a frantic feline version of musical chairs, and when the music stopped, it was every cat for him-or-herself.

This was my first clue that the first nip of autumn was in the air and that flannel sheet season was nigh. My second clue was the “prime time” prominence of fall constellation Capricornus the Sea Goat, which can be seen approaching the meridian from the east about an hour after sunset, when the sky’s just gotten good and dark. It will soon dislodge Sagittarius the Archer— just leaving the meridian, heading west— from its summertime domination of our view to the south.

Capricornus (kapp-rih-KORN-uss) is one of the twelve constellations of the zodiac. This band of constellations is significant because it straddles the ecliptic, the imaginary line that represents the path the Sun appears to take across the sky, as seen from Earth. Because the Earth, Moon, and planets all lie in roughly the same plane as they orbit the Sun, we see the Moon and the planets stick close to the ecliptic as they cross our sky.

You might say the ecliptic represents the plane of our platter-shaped solar system. But I like to think of it, and the zodiacal constellations that encompass it, as the celestial parade route upon which I’m sure to see a procession of planets float by.

Case in point: there are currently two planets passing through Capricornus, Jupiter and Neptune. Jupiter is easily seen with the naked eye; it’s the blazing “star” in the southeastern sky and the first luminary that pops out at you after sunset. Right now you can use Jupiter to help pinpoint the location of Capricornus, should you be unfamiliar with its star pattern.

Viewing Neptune (not a naked-eye object) requires a star map or software application that shows current planet positions, and large binoculars or a telescope.

Star map created with Your Sky

About an hour after your local sunset time, locate bright Jupiter. Using the map above and the relative position shown for Jupiter, trace out in the sky the star pattern shown. This is the asterism (recognizable star pattern) known as the Bandanna, and it contains the brightest stars in Capricornus.

Capricornus in Johannes Hevelius's 1690 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

Trust me, you’re far more likely to learn to recognize a stellar bandanna than a sea goat. I like Mesopotamian and Greek mythology— and tales of animal metamorphosis— as much as the next person. But honestly, what sort of perverse storyteller would find it necessary to graft a fish’s tail onto the head and body of a goat? It's so grotesque as to defy understanding, so perhaps we should just wave the white bandanna of surrender.

~ ~ ~ ~ ~

Here in the valley of the Rio Grande, the first nip of autumn means sweet relief from stifling summer heat along with the sweet smell of roasting New Mexican chiles. It also means I’ll be harvesting one of my favorite deep-sky objects from the telescopic depths of Capricornus. More on that later. Right now, I’ve got to air out my cozy flannel sheets and clean my high-power eyepiece.

Sweet.

Astronomy Essential: The four gas giant planets don’t have solid surfaces.

It’s hard to comprehend that no interplanetary traveler of the future will ever step out onto the surface of Jupiter or Saturn— even with the right protective space suit. Those gas giants are, as the name suggests, composed of gasses: primarily the elements hydrogen, helium, methane, ammonia, and oxygen.

On the two gas giants farthest from the Sun, Uranus and Neptune, the normally gaseous elements are believed to take liquid or semi-solid form. Gas-infused slush and frigid “seas” of liquid hydrogen, helium, methane, and ammonia make these two ports of call no less inhospitable than their vaporous neighbors.

Cassie's Cluster

2009-09-10T23:18:00.011-06:00

Note: There will be no September 17 post so that I may prepare for the STAR-HOPPERS weekend workshop in astronomy for grandparents & grandkids. Enjoy the September 10 post or browse my older posts. I'll be back with a new post on September 24.

Messier 52 in the constellation Cassiopeia the Queen is one of my favorite open clusters. I like its rich star field and its somewhat fan-shaped appearance. I also consider it a big plus that it’s easy to find.

An open cluster is a loose collection of stars that formed around the same time in the same nebula (cloud of gas and dust). You might think of an open cluster as a sort of family group.

Messier 52, or M52 as it is commonly known, is one of the 110 celestial objects in the catalog of famed 18th century French astronomer and comet-hunter Charles Messier (pronounced MESS ee yay). This catalog is used extensively by amateur astronomers as an observing list, since it contains some of the “best and brightest” deep-sky objects in the night sky. Messier discovered M52 in 1774, while “chasing” a nearby comet.

M52 is easy to find because you can use the distinctive Lazy W asterism (star pattern) of Cassiopeia to locate it. Grab your binoculars, and let’s take a look at Cassie’s cluster.

1) About an hour after your local sunset time, face north. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your left shoulder to the west, and you’ll be facing approximately north.

Looking north to Cassiopeia's Lazy W
Star maps created with Your Sky

2) Look for a W-shaped group of stars east of the meridian. This is the central asterism of Cassiopeia, the Lazy W. Cassiopeia is a circumpolar constellation, one that circles the North Celestial Pole, the imaginary fixed point in the sky directly above the North Pole. Luckily for us, there is a star extremely close to that point in the sky, which serves as a navigational marker. This is Polaris, the North Star.

Cassiopeia and the other circumpolar constellations appear to make a complete counterclockwise circuit around the North Star, over the course of one day. But they’re not really spinning around the North Star. This apparent motion, or the way they appear to move in our sky, is caused by the rotation of the Earth, as it spins on its axis like a top, 24/7.

3) From Shedar (SHEDD-er), the lower right star of the W, draw an imaginary line through Caph (KAFF), the upper right star of the W. Then extend that line the same distance again past Caph, plus a skosh. Train your binoculars on that spot, and you should see a fuzzy patch. With a small telescope, you’ll be able to resolve the stars in the cluster, that is, they’ll separate into distinct points of light.

M52 lies around 5,000 light years from Earth. One light year is the distance light travels in one Earth year, nearly six trillion miles. The cluster is estimated to contain 200 members.

The open cluster M52
Credit: AURA/NOAO/NSF

Two hundred family members in one place at the same time makes for quite a reunion. Pass the potato salad, please.

Astronomy Essential: The universe began with the Big Bang.

The Big Bang is a widely accepted scientific theory of the origin of the universe. It postulates that about 13.7 billion years ago, the visible universe was extremely dense and extremely small— about the size of a dime. This singularity suddenly expanded to create the large-scale universe, which continues to expand today.

Many astronomers accept that a Big Bang event is the best current explanation for some key observable features of the universe, such as: its continuing expansion from a smaller, denser state; the microwave radiation “glow” that is present throughout the universe; a consistent abundance of simple elements such as hydrogen and helium throughout the universe, even in the oldest objects; and a limit on the age of stars in the cosmos.

Horse Trade

2009-09-03T20:52:00.014-06:00

In addition to the center of the galaxy, the spout of the Teapot asterism in the constellation of Sagittarius the Archer points to a whimsical naked-eye object in the Summer Milky Way. This object requires a dark sky to see it, but it’s worth a trip away from city lights.

The object is actually a two-fer, two objects in one economical package. Both are dark nebulas, and they lie across the “star river” of the Milky Way from the Teapot, in neighboring Ophiuchus the Snake Handler.

Dark nebulas (NEBB-yoo-luhs) were once thought to be empty areas in the sky where no stars existed. Now we know they are areas of thick dust— dust so dense it obscures the light of the stars behind it. Dark nebulas are sometimes named for the objects they resemble. It is human nature, after all, to attribute patterns or meaning to random visual events, for example, seeing animals or faces in clouds. This practice even has a name: pareidolia (pronounced pear-eye-DOH-lee-uh).

The first of our two objects is a dark nebula called the Pipe Nebula. You can see from the image below that it looks like the stem and bowl of a smoker’s pipe. This will be the easier of the two shapes to pick out.

For our second object, the Pipe becomes the hindquarters of a horse, and his front half extends away from the Milky Way, as shown in the next image. This is commonly known as the Prancing Horse Nebula.

You should be able to make out the equine's torso and head, as well as his raised front leg.

Here in the American Southwest, this object is more commonly known as the Burro Nebula, or simply the Burro. Burro is derived from the Spanish word for donkey and usually refers to the undomesticated version of that animal. There’s a wild burro population of about 3,800 in the American West. These animals are the descendants of those first introduced into the desert Southwest by the Spanish in the 1500s.

The Burro, with lowered head and upraised leg on the right, hindquarters on the left.

The glowing star cloud above him makes it look as though he is carrying a pack.
© T. Credner & S. Kohle, AlltheSky.com

You can have your prancing horse. I’ll stick with my burro. He eats a lot less.

Astronomy Essential: The Earth’s magnetic field protects us from the solar wind.

The Earth is a magnetic object, that is, it acts like a magnet, because it has an iron core. As with any magnet, the Earth generates a magnetic field that surrounds it. This magnetic field is called the magnetosphere.

The magnetosphere deflects the solar wind generated by the Sun. The solar wind is a stream of charged particles traveling at over one million miles per hour. Without the magnetosphere to protect it, Earth’s atmosphere would be vaporized by the solar wind.

Tea Party

2009-08-27T21:28:00.014-06:00

Last week we located the Teapot, the picturesque asterism (star pattern) in the constellation of Sagittarius the Archer, and the nearby spot that marks the center of our Milky Way galaxy.

Now let’s take a closer look at the stars that make up the Teapot pattern.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Star maps created with Your Sky

2) Look for the teapot shape low over the southern horizon and a little bit northeast of the Scorpion’s stinger. The Teapot is oriented with its curving handle on the eastern (left) side and the spout pointing toward the Scorpion on the right.

3) Let’s start at the top of the Teapot’s pointed lid. The star marking that spot is Kaus Borealis (KOWSS bore-ee-AL-iss), a blend of Arabic and Latin that means the northern bow, a reference to the Archer's weapon of choice. Kaus Borealis is an orange giant star.

Continuing clockwise around the Teapot, we next come to Kaus Media (KOWSS MAY-dee-yuh), Arabic and Latin for the central bow. Kaus Media is also an orange giant star.

4) Next in line is Alnasl, at the point of the spout. Alnasl (all-NAH-zull) is from the Arabic for the arrow’s point. And you may recall from my previous post that Alnasl points the way to the galactic center. Do you get my point?

5) At the bottom right corner of the Teapot’s base is Kaus Australis, the brightest star in Sagittarius. Kaus Australis (KOWSS aw-STRAH-liss) is Arabic and Latin for the southern bow. Kaus Australis is extremely bright, around 375 times more luminous than our Sun. There is some debate about its color; it may be either a blue or a white giant star.

Now you know the trinity of stars (Kaus Borealis, Media, and Australis) that delineates the curve of the Archer’s bow. But this is no ordinary two-legged archer. The ancient figure of Sagittarius is a bow-and-arrow-wielding centaur; a centaur is a mythological four-legged creature that’s half human, half horse.

Sagittarius in Johann Bode’s 1801 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

6) The bottom left corner of the Teapot’s base is marked by Ascella (uh-SELL-uh), Latin for armpit. Ascella is a binary system, that is, two stars in orbit around each other. Both of Ascella’s component stars are white stars of nearly the same brightness. With the naked eye, we see their combined light as one star.

7) The lower star on the Teapot’s handle has no traditional name, so we call it Tau for its Greek-lettered star catalog designation. The upper star, however, is Nunki, the second brightest star in Sagittarius. The name Nunki (NUNN-kee) is of Sumerian origin, and it may have something to do with a holy city in the sky. Nunki is a blue-white dwarf star.

Finally, where the upper end of the handle attaches to the Teapot is Phi, another star with no traditional name.

8) Do you take milk with your tea? If so, you’re in luck. Just connect the dots of Ascella, Tau, Nunki, Phi, and Kaus Borealis to make the asterism known as the Milk Dipper.

And to stir your fragrant libation, use the Teaspoon, the dainty four-star asterism that looks like a spoon viewed from the side. It’s floating northeast of the Teapot’s handle, at the ready.

Astronomy Essential: Massive stars die in supernova explosions.

Stars much more massive than our Sun typically die in cataclysmic explosions called supernovas.

A massive star evolves through nuclear fusion into an onion-like structure of layered, increasingly heavy elements terminating with an iron core. Eventually, the iron core collapses and violently rebounds, creating a shock wave that blasts the surrounding stellar material outward.

The resulting cloud of gas and dust— which contains the elements necessary for human life— expands into space and is eventually recycled into new stars.

The Center of the Galaxy

2009-08-20T21:41:00.014-06:00

Of the many naked-eye, binocular, and telescopic treasures to be found in the summer constellation Sagittarius the Archer, none fires the imagination like the one we can’t actually see.

Just off the spout of the Archer’s central asterism, the Teapot, lies the spot that marks the direction of the center of the Milky Way, our home galaxy. An asterism is a recognizable star pattern, and the Teapot is a prime example of why amateur astronomers use asterisms to navigate the sky, not ancient, obscure constellation patterns.

I defy anyone to spot a centaur sporting a bow and arrow in the jumble of stars that is Sagittarius. But happily, the brighter stars in that region of the sky collectively resemble a teapot, an object with which we are perhaps a bit more familiar. The softly glowing billows of the Summer Milky Way intersect with the Teapot in a way that suggests steam vigorously issuing from the spout.

We can’t see the center of our galaxy in visible light because of the obscuring dust that lies between us and the galactic core. However, astronomers use cameras that operate in the infrared and radio wavelengths of light in order to “see” past that dust.

Composite image of the center of the Milky Way, in visible and infrared wavelengths
Credits: NASA, ESA, Q.D. Wang (University of Massachusetts, Amherst), Jet Propulsion Laboratory, and S. Stolovy (Spitzer Science Center/Caltech)

Try to observe from a dark site, away from urban light pollution, so you can enjoy the picturesque “steam” rising from the Teapot.

Star map created with Your Sky

3) The galactic center lies in the glowing band of the Milky Way, our edgewise view of our platter-shaped galaxy. As shown on the star map, the Teapot’s spout points the way.

Since our eyes aren’t up to the task of penetrating the thick dust separating us from our quarry, we’ll just have to use our imagination. We can imagine the massive cluster of stars that congregate at the bustling galactic core. We can imagine the star-strewn pinwheel-shaped arms of our spiral galaxy radiating out from that core. And if we squint, perhaps we can even imagine the supermassive black hole that lurks at the heart of our home galaxy, a reassuringly distant 26,000 light years away.

Astronomy Essential: Visible light is just a small portion of the electromagnetic spectrum.

Light is a form of energy that travels in different wavelengths. Collectively, these different wavelengths of light are called the electromagnetic spectrum. Separately, we know them as gamma rays, X-rays, ultraviolet or UV, visible light, infrared, microwave, and radio. Gamma rays have the shortest wavelength and radio has the longest wavelength, up to several miles in length.

Notice that visible light, what we humans can see, represents just one wavelength on the electromagnetic spectrum. That is why astronomers use cameras with special detectors to capture data from the other wavelengths— the ones that remain hidden to our eyes.

Can you imagine a species that could see in all wavelengths of light?!

The Snake Handler

2009-08-13T21:58:00.019-06:00

We continue our exploration of the prominent summer constellation Ophiuchus the Snake Handler (oh-fee-YOO-kuss) with a closer look at the stars that make up its central asterism, the Coffin.

Asterisms are recognizable star patterns that help us navigate around the sky and figure out which constellation we’re in. The Big Dipper is an example of a more well-known asterism; it’s a star pattern within the constellation of Ursa Major the Big Bear.

Although the largest summer constellation, Ophiuchus is virtually unknown except among seasoned sky observers. Perhaps its difficult spelling and pronunciation have something to do with that. Perhaps it pales in comparison to neighboring constellations Scorpius the Scorpion and Sagittarius the Archer, which are each favored with brighter stars and more distinctive star patterns that really jump out at the observer. And perhaps it’s a conspiracy perpetrated by astrologers.

OK, just kidding on that last one. But it is interesting to note that Ophiuchus is, in effect, the thirteenth sign of the zodiac. The zodiac is the daisy chain of constellations that encompasses the paths the Sun, Moon, and planets take across the sky, as seen from Earth. In addition to the 12 conventionally-known zodiacal constellations, the Sun, Moon, and planets travel through Ophiuchus. And there have certainly been babies born while the Sun was in Ophiuchus. Yes, there are some Snake Handlers out there masquerading as Archers and Scorpions.

The band of the zodiac
Diagram by Dr. Guy Worthey

Looking south to Scorpius and Ophiuchus
Star maps created with Your Sky

2) Locate the distinctive curve of the scorpion’s body, just above the southern horizon. Ophiuchus essentially rides on the back of the scorpion. So look north of the scorpion for the large Coffin asterism, which comprises the brightest stars in Ophiuchus. It’s known as the Coffin because it resembles an old-fashioned casket with a pointed head.

The stars of the Coffin asterism

3) The brightest star in Ophiuchus marks the pointed top of the Coffin. Its name, Rasalhague, comes from the Arabic for head of the serpent collector. Rasalhague (RAH-sahl-hayg) is a white giant star, as much as four times more massive than our Sun.

4) Moving counterclockwise around the Coffin from Rasalhague, we next come to Cebalrai, an orange giant star. Cebalrai (SEH-buhl-rye) is from the Arabic for the shepherd’s dog, a reference to an ancient Arabic tradition that saw that part of the sky as a pasture.

5) Next we come to Sabik, at the base of the Coffin. Sabik (SAH-bick) is the second brightest star in Ophiuchus, and its name is from the Arabic for the leading one. Sabik is a binary, that is, two stars in orbit around each other. In this case, both stars are white and of nearly the same brightness. Although we are seeing the combined light of two stars when we look at Sabik, it appears to the naked eye as one star.

6) The star in the middle of the Coffin’s base has no traditional name, so we call it Zeta after its star catalog designation. Zeta is a blue-white dwarf star. The next Coffin star, marking the western corner of the base, is Yed Prior. Yed Prior, a combination of Arabic and Latin, means the foremost hand. This star marks the left hand of the snake handler, the one that grasps the snake’s head. Yed Prior is a red giant star.

7) Finally, we complete the Coffin back up at the pointed end with Kappa, another star with no traditional name and known only by its star catalog designation. Kappa is a white star.

For a look at a few of the Snake Handler’s deep-sky delights for binocular and telescope viewing, visit my previous post and the one before that.

Ophiuchus in John Flamsteed’s 1729 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

Those of you in the health care field may be interested to know that in Greek mythology, Ophiuchus was identified with Aesculapius (ess-kyoo-LAY-pee-yus), the god of medicine. Perhaps there is an ancient connection between Ophiuchus/Aesculapius and his sinuous snake, and the caduceus (kuh-DOO-shuss)— the staff with two entwined snakes that has come to symbolize a physician.

A caduceus
Drawing by Rama and Eliot Lash

Astronomy Essential: One fifth of the world’s population can’t see the Milky Way.

Light pollution— excessive and inappropriate use of artificial night lighting— has impacted humankind’s view of the night sky. One-fifth of the world’s population can no longer see the glowing band of the Milky Way, because the sky is washed out by artificial light, much of it directed upwards. This phenomenon is at its worst in the United States, where two out of three residents cannot be inspired and awed by a view of their home galaxy.

Using properly shielded light fixtures that direct light only onto the ground, where it is needed for safety and security, is one effective solution to the problem.

Gobs of Globs

2009-07-30T23:30:00.014-06:00

Note: There will be no August 6 post so that I may prepare for a She Is An Astronomer outreach event. Enjoy the July 30 post or browse my older posts. I'll be back with a new post on August 13.

Last week we looked at a bright open cluster in the summer constellation Ophiuchus the Snake Handler. Now let’s look at a different type of star cluster of which Ophiuchus contains a plethora: the globular cluster.

Globular clusters, or “globs” as they are commonly known, are dense balls of gravitationally bound stars. There are at least 150 known globs in our home galaxy, the Milky Way. Globs contain tens of thousands to millions of stars.

A number of the brighter globs that can be spotted from the Northern Hemisphere are found in the Messier catalog (MESS-ee-yay). This is the catalog of deep-sky objects compiled by the famed 18th century French astronomer Charles Messier, who observed from the rooftops of Paris. The Messier catalog contains some of the finest binocular and telescope objects in the night sky and is widely used by amateur astronomers as an observing list.

With seven each, Ophiuchus (oh-fee-YOO-kuss) and Sagittarius contain more Messier globular clusters than any other constellation.

If you’re not sure how to locate Ophiuchus, read last week’s post. The map below shows the locations of the Messier globs that call the Snake Handler “home.” Try spotting them with binoculars from a dark site, orienting from the Coffin asterism in Ophiuchus. Most should be visible as small fuzzy balls in modest-sized binoculars like 7x35s or 7x50s. The globs M9 and M107 will be tough to impossible, so don‘t bother with those. Use the binocular targeting tip I’ve discussed before.

The Messier catalog globular clusters in Ophiuchus
Star maps created with Your Sky

Now try observing them all with a telescope, if you have one. Depending on how much aperture (diameter of your primary lens or mirror) you have, you’ll either see a larger, brighter fuzzy ball or you’ll begin to resolve the cluster, that is, separate the stars into distinct points of light. Once resolved, you’ll see why I call globular clusters “galactic sugar piles.”

One theory among astronomers is that globs are the cores of ancient galaxies that collided with the Milky Way. All the outer stellar material was ripped from the galaxies and shredded by our home galaxy's powerful gravitational force. What remains are the densely star-packed galactic cores, studding the Milky Way like trophies on a hunter’s wall.

It’s a jungle out there.

Astronomy Essential: There is gravity in space.

There is gravity everywhere, since it's produced by all objects with mass in the universe. Its force, however, decreases with distance.

The “weightlessness” or “Zero G” (zero gravity) that an astronaut experiences in space is caused by the balancing act between the centrifugal force on his body and the gravitational force on his body.

In other words, Earth’s gravity— although a little weaker at that distance— is still pulling him towards the planet. However, the centrifugal force of his orbiting spacecraft propels him outward, away from the center of rotation (Earth), thus canceling out the effect of the gravity.

Caroline and the Cluster

2009-07-24T00:38:00.010-06:00

If you ask an amateur astronomer to name a famous female astronomer, the first one who leaps to mind will most likely be Caroline Herschel (1750 to 1848). Sister to the renowned astronomer and Uranus discoverer William Herschel, she was an accomplished observer in her own right.

Although born in Germany, William and Caroline emigrated to England, where William became the royal astronomer to King George.

Caroline’s discoveries included eight comets; in fact she was the first woman to discover a comet. She also discovered 14 deep-sky objects, and she catalogued many stars and nebulas. The diminutive Caroline’s primary instrument was a modest-sized reflecting telescope, around four inches in diameter.

Let’s take a look at the brightest deep-sky object she discovered: the open cluster IC 4665 in Ophiuchus the Snake Handler. It is appropriate that we search for it in July, as she discovered it on July 31, 1783.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Looking south to Scorpius and Ophiuchus
Star maps created with Your Sky

2) Locate the distinctive curve of the scorpion’s body, just above the southern horizon. Ophiuchus (oh-fee-YOO-kuss) is a large constellation that essentially rides on the back of the scorpion. So look north of the scorpion for a large asterism (star pattern) known as the Coffin, which comprises the brightest stars in Ophiuchus. It’s known as the Coffin because it resembles an old-fashioned casket with a pointed head. We’ll take a closer look at the Coffin stars in a future post.

The Coffin asterism of Ophiuchus with open cluster IC 4665

3) Point your binoculars or small-aperture telescope just above the star Cebalrai (SEH-buhl-rye) near the top of the Coffin. You don’t want to use a large-aperture (large-diameter) telescope or a lot of magnification for an object like this with a large apparent size (the amount of sky it covers from our perspective on Earth).

Can you spot the open cluster IC 4665? An open cluster is a loose collection of stars that formed around the same time in the same nebula (gas and dust cloud). You might want to think of an open cluster as a sort of family group. IC 4665 has around 30 members in its family.

Open cluster IC 4665

Image credit: Digital Sky Survey

Hats off and a tip of the teapot to Caroline Herschel, astronomer.

Astronomy Essential: Shooting stars are meteors.

The phenomenon we call a “shooting star” is actually a bit of space rock or dust called a meteoroid burning up as it enters Earth’s atmosphere. The streak of light produced as the meteoroid is incinerated is called a meteor. Most meteoroids are very small: the size of grains of sand or grains of rice. It is the high entry velocity of the particles that produces the lovely light show.

Occasionally, larger meteoroids will survive their high-speed encounter with Earth’s atmosphere and hit the ground; these rocks are known as meteorites.

Moonwalk

2009-07-16T22:28:00.015-06:00

Monday, July 20, 2009 marks the 40th anniversary of the first Moon landing. It’s hard to believe it’s been only 40 years since astronauts Neil Armstrong and Buzz Aldrin left their historic footprints on the Moon. It seems like eons ago, although I’m not sure why. Perhaps it’s because so much has transpired since then in the arena of space exploration.

Source: NASA

Humankind has launched numerous space exploration missions since 1969, taking our technology, if not our bodies, to the edge of our solar system. Add to that the prolific output of the Hubble, the Chandra, and the Spitzer space telescopes: spectacular, surreal images of deep-space objects in the Milky Way, along with those beyond our home galaxy, billions of light years away.

Sometimes it feels as if I’m comfortably seated on the observing deck of a swift spacecraft, while brilliant scientists and engineers sweat it out in the boiler room in order to incrementally extend my view out the picture window.

Of course, my little conceit stems from our common, virtual experience of space. We are for the most part a species of armchair travelers, exploring the universe from the comfort of terra firma. Just a few brave souls suit up to ride rockets to the International Space Station and back. Only six times have humans landed on the Moon. Only six times have any of us looked back at Earth while standing on another world.

In 40 years, yes, our vision has penetrated far into the universe. But our footprints have not.

The Sea of Tranquility provided the site for the historic Apollo 11 moon landing in July 1969. You can easily spot this large dark feature, a lava-filled crater, with the naked eye.

Give it a try when the Moon is waxing (growing).

Astronomy Essential: A galaxy is a large system of stars and planets, bound by gravity and rotating around a dense core.

The word galaxy (GA-leck-see) derives from the Greek word for milk. Galaxies are typically categorized by their shape and/or their orientation to Earth. Some of the shape-based categories are spiral (like our home galaxy, the Milky Way), elliptical, lenticular, and irregular. Common orientation categories are face-on and edge-on.

There are an estimated 200 billion galaxies in the universe.

The Riddle of the Snake

2009-07-09T23:13:00.022-06:00

Fans of astronomy trivia may know the answer to this riddle: what’s the only constellation that is both one and two?

Answer: Serpens the Snake. The celestial snake imagined by the ancients struggles in the unyielding grasp of Ophiuchus the Snake Handler, winding between his legs. When 20th century astronomers were laying out the boundaries of the modern constellations, they kept the ancient figure of Ophiuchus (oh-fee-YOO-kuss) intact and divided Serpens into two parts: the head, on the Snake Handler’s left, and the tail, on the Snake Handler’s right. Thus the intertwined figures of old begat the only modern constellation with two disconnected parts.

Ophiuchus and Serpens in John Flamsteed’s 1729 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

Modern constellation boundaries of Ophiuchus and Serpens (in green)
Star maps created with Your Sky

Let’s aim for the head.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Looking south

2) Just under the horseshoe-shaped asterism (star pattern) of the constellation Corona Borealis (which is located on or near the meridian) and east of the bright star Arcturus, look for a small triangle of stars. This is the head of the snake. If your vision is keen and your skies dark, you may also spot the two fainter stars above the triangle. Add them to the other three and you’ll have an “X” that marks the spot where the snake’s head lies.

3) Due south of the snake’s head is a star that’s brighter than any of the “X” stars. This is Unukalhai (uh-NOO-kuh-lye), an orange giant and the brightest star in Serpens. Unukalhai is from the Arabic for serpent’s neck, the star’s location in the snaky figure of antiquity.

4) This section of Serpens containing the head and the neck is known as Serpens Caput, to distinguish it from Serpens Cauda, the section east of Ophiuchus. Serpens Caput (SIRR-penz KAH-put) is Latin for snake head, while Serpens Cauda (SIRR-penz COW-duh) is Latin for snake tail.

Serpens Cauda is a tail for another day.

Astronomy Essential: A nebula is a cloud of gas and dust in space.

The word nebula (NEBB-yoo-luh) is from the Latin word for cloud. In general, there are four types of nebulas or nebulae (NEBB-yoo-lee): diffuse nebulas, planetary nebulas, supernova remnants, and dark nebulas.

Diffuse nebulas are stellar nurseries, gas and dust clouds where stars are born. Planetary nebulas are the remains of average-sized stars (like our Sun) that have died. Supernova remnants are the remains of massive stars that died in cataclysmic explosions. Dark nebulas are gas and dust clouds where the dust is so thick it completely obscures the light from the stars behind it.

A Pair of Ragged Claws

2009-07-02T20:57:00.018-06:00

One of the signature sights and true delights of summer stargazing is the curvy constellation Scorpius. But preceding the scorpion in the sky are its long-lost appendages: the Claws. It was the ancient Romans who reportedly hacked them off in order to make a twelfth zodiac sign, Libra the Scales.

Scorpius and Libra in Alexander Jamieson’s star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

Let’s reunite the celestial arachnid with its pincers.

Looking south to Libra
Star maps created with Your Sky

2) Just to the right (west) of the arc of stars that marks the scorpion's head is a quadrilateral of stars— two bright and two dim. The brighter ones mark the tips of the Claws. The bright one closest to the southern horizon is the star Zubenelgenubi (zoo-BENN-uhl-jenn-NOO-bee). Its name is from the Arabic for southern claw. It’s actually a double star that may be “split” with the naked eye, that is, you should be able to see the stars as two separate points, if you have relatively good eyesight and you’re in a dark location that’s relatively free of light pollution.

"The Claws" in Libra

3) The slightly brighter star above Zubenelgenubi is the blue-white dwarf star Zubeneschamali (zoo-BENN-esh-uh-MAH-lee), from the Arabic for northern claw. The luminous Zubeneschamali is about 130 times brighter than our Sun.

4) Of the two dimmer stars in the quadrilateral, only the southern one has a traditional name: Zubenhakrabi. Zubenhakrabi (zoo-BENN-hock-RAH-bee) is from the Arabic for scorpion’s claw. It’s a red giant star.

We call the northern star Gamma, for its star catalog designation. Gamma is an orange star.

It's interesting to note that Libra is the only constellation of the zodiac that represents an inanimate object. It may also be the only constellation whose brightest stars present a devilishly difficult trio of tongue twisters.

Astronomy Essential: Gravity has shaped our universe.

Gravity is one of the four fundamental forces known in the universe. Although the weakest of the four, it has shaped the large-scale structure of our universe by initiating star and galaxy formation.

Gravity pulls objects together. Every object produces a gravitational force that attracts all other objects. The more mass (quantity of matter) an object has, the stronger its gravitational force.

The gravity that causes a gas cloud in space to compress until it becomes a star is the same force that keeps us attached to the surface of planet Earth. The gravity that causes stars to congregate into massive collections called galaxies is the same force that keeps Earth in orbit around the Sun.

The Star-Formerly-Known-as-Pole

2009-06-26T00:05:00.010-06:00

Snaking along the long body of Draco the Dragon from his head, which we examined in last week’s post, we eventually come to a fairly faint naked-eye star opposite the bowl of the Little Dipper. This is the notable star Thuban.

The name Thuban (THOO-bahn) comes from the Arabic for serpent. Because of the star’s importance to ancient cultures, however, it has born many other names: “Judge of Heaven,” “Proclaimer of Light,” “Crown of Heaven,” and “High One of the Enclosure of Life,” to name a few.

Looking north to Draco and the Dippers
Star maps created with Your Sky

Thuban’s ancient significance stemmed from the fact that it was once the North Star, marking the position of the North Celestial Pole. The North Celestial Pole is the imaginary fixed point in the sky that the Earth's axis would intersect, were it extended from the North Pole into space. The North Star, because it marks geographic north, has been important throughout the ages for navigation.

We are accustomed to the star Polaris, which marks the end of the handle of the Little Dipper, being our North Star. It seems odd at first to think that another star might have been the North Star or Pole Star long ago. In fact, Polaris won’t continue to be our North Star forever. This phenomenon is caused by precession, the change in the alignment of Earth’s axis.

Because the spinning Earth wobbles slowly over time, our axis doesn’t always point at the same spot in the sky. This wobble is caused by gravitational tugging by both the Sun and the Moon. The result is that the position of the North Celestial Pole--where Earth’s axis points--moves over time against the backdrop of the stars, completing a circle in about 26,000 years. The North Celestial Pole will pass closest to Polaris around the year 2100, after which it will begin to move away from it.

The good news is, if we wait just 26,000 years, Polaris will be our North Star once more. What goes around, comes around.

Astronomy Essential: Space is extremely cold.

Intergalactic space, the regions of space that lie between galaxies, is an inhospitable minus 455 degrees Fahrenheit.

Compare that to absolute zero, the coldest theoretical temperature, which is minus 459.67 degrees Fahrenheit, not much colder.

The Sleeping Dragon

2009-06-18T23:37:00.013-06:00

Well placed in the northern sky during spring, the constellation of Draco the Dragon winds sinuously between the Big and Little Dippers in the constellations of, respectively, Ursa Major and Ursa Minor. Although the Dippers are among the most-viewed asterisms (recognizable star patterns) in the night sky, Draco often goes unnoticed.

Dare we wake the sleeping dragon?

Draco in J. Middleton’s 1842 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

1) About an hour after your local sunset time, face north. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your left shoulder to the west, and you’ll be facing approximately north.

Looking north to the Dippers and Draco
Star maps created with Your Sky

2) Locate the Big Dipper in Ursa Major and the Little Dipper in Ursa Minor. Midway between the bowl of the Little Dipper and the very bright star to the east, Vega in the constellation Lyra, is a quadrilateral of fainter stars. This is the asterism known as the Lozenge, and it marks the head of Draco (DRAY-koh).

3) The brightest of the four corner stars of the Lozenge is the orange giant Eltanin. Eltanin (ELL-tuh-ninn) is from the Arabic for serpent. Moving counterclockwise around the Lozenge from Eltanin, we next come to the yellow supergiant star Rastaban. Rastaban (RAH-stuh-bahn) is from the Arabic for serpent’s head.

The Lozenge asterism in Draco

The third corner star in our roundabout has no traditional name, so we call it Nu (NOO) for its star catalog designation. Nu is a binary system, two stars— in this particular case, both white stars— in orbit around each other. With the naked eye we see their combined light as one star. If you have binoculars, use them to look at Nu. You should be able to spot the nearly identical pair.

The orange giant Grumium completes our dragon’s head. Grumium (GROOM-ee-yum) is from the Latin for snout.

The Lozenge asterism was so-named not because it resembles a cough drop, but rather because a lozenge is a diamond-shaped figure. Granted, the misshapen boundaries of this dragon’s head can only be described as a diamond in the rough.

Astronomy Essential: A star's visible color depends on its surface temperature.

Although star color is sometimes subtle, we can observe it, especially when we’re comparing two stars of different colors. Stars that look red, orange, or coppery are at the cool end of the stellar temperature range. White, yellow-white, and yellow stars are in the middle of the range. Our Sun is a yellow star.

The stars at the hot end of the temperature range appear blue and blue-white, the former being the hottest. The average temperature of a blue star ranges between 56,000 and 87,000 degrees Fahrenheit. Now that’s hot.

The Heavenly Herdsman

2009-06-11T23:15:00.028-06:00

The name Bootes (boh-OH-teez) is believed to derive from ancient Greek words for ox and driver. Translation into other languages rendered ox-driver as herdsman, and so we’ve come to know this prominent spring constellation as Bootes the Herdsman.

You won’t find the Herdsman’s oxen in the sky. He was, however, associated with the nearby Big Dipper, what the Greeks called “the wagon.” It is this wagon that was reportedly being pulled by Bootes’ celestial oxen.

In a number of classical star atlases, Bootes is depicted as holding the leashes of a pair of hunting dogs: the constellation known as Canes Venatici (KAY-neez vee-NATT-uh-sigh). The hunting dogs are straining at the end of their leashes as they pursue nearby Ursa Major (ER-suh), the Big Bear. The Big Dipper is the central asterism (recognizable star pattern) in the constellation of Ursa Major.

Bootes and the Hunting Dogs in John Flamsteed's 1729 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

During spring and summer, when Bootes is prominent in the sky, you’ll notice that he and his dogs, well, dog the Big Bear across the sky as it circles the North Star counterclockwise. The Big Bear is one of the circumpolar constellations, which means it circles the North Celestial Pole, the imaginary fixed point in the sky that the Earth's axis would intersect, were it extended northward. The North Star, Polaris, just happens to lie at the North Celestial Pole, which is why the circumpolar constellations appear to circle the North Star.

Let’s follow the herd.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Arc to Arcturus
Star maps created with Your Sky

2) Tilt your head all the way back and look up at the zenith, the point directly overhead. Locate the Big Dipper, a little north of the zenith. Following the curve of its handle, arc to Arcturus, the brightest star in Bootes.

Big and brilliant, the orange giant star Arcturus is 25 times the diameter of our Sun and 113 times as luminous. Arcturus is Greek for guardian of the bear, a reference to the star’s ancient association with— and apparent trailing of— neighboring Ursa Major. Can you discern its golden or copper hue?

3) Now that you’ve found Arcturus, you can trace out one of my favorite asterisms: the Ice Cream Cone. I’ve a profound weakness for ice cream, so locating this delicious asterism is a sort of guilt-free indulgence.

Ice Cream Cone asterism in Bootes

Most of the bright stars in Bootes form the Ice Cream Cone. Arcturus is the bottom of the pointed cone. Moving north from the point, you’ll come to two stars that form the top of the cone. The one on the left (east) is the orange giant Izar, the second brightest star in Bootes. Izar (EYE-zahr) is from the Arabic for loin cloth. The one on the right (west) has no traditional name, so we call it Rho (ROE) for its star catalog designation. Like Arcturus and Izar, Rho is an orange giant star.

4) Continuing north, we are rewarded with a mound of sweet, cold confection bounded by the stars Delta, Nekkar, and Seginus, moving from east to west. Delta is the star catalog designation for this yellow giant with no traditional name. Nekkar (NECK-ahr) is from the Arabic for ox-driver. Nekkar is another yellow giant star.

Did you ever play the group game “Telephone” when you were a kid? The first kid in a line or circle of kids would whisper a phrase to the kid next to him. That kid would whisper it to the next kid, and so on. The last kid would say out loud the phrase she’d heard. By the time it got to the end of the line, the phrase was invariably garbled, sometimes beyond recognition.

That’s sort of what happened with our third ice-cream-mound star, the white giant Seginus. Believe it or not, the name Seginus (segg-EEN-uss) started out as the Greek name Bootes! It was first mangled in translation by the Arabs. Then the Arabic wrong name was corrupted again by the Romans into a Latinized form. So the name that filtered down into modern times, Seginus, is pretty much meaningless.

Except of course to us, because we know it’s just Telephonese for ox-driver.

Astronomy Essential: Hydrogen is the most abundant element in the universe.

Hydrogen is estimated to make up a whopping 75% of the visible matter in the universe.

Hydrogen is the simplest chemical element. A hydrogen atom is composed of just one proton at the nucleus (core) and one electron in orbit around the nucleus. A proton is a particle with a positive electrical charge, while an electron is a particle with a negative electrical charge.

Stable hydrogen nuclei are believed to have formed only three minutes after the Big Bang. It took another 700,000 years or so for the nuclei to collect their electrons and become stable atoms. Hydrogen was the most abundant element in the universe back then, too.

Hydrogen is the fuel that powers stars. Hydrogen burns into helium in the cores of stars, and this nuclear reaction produces energy in the form of heat and light.

After oxygen and carbon, hydrogen is the third most common element in the human body. It is a primary component of water, and our bodies are composed of more than 50% water. Without hydrogen, human life as we know it could not exist.

As the Crow Flies

2009-06-05T17:12:00.015-06:00

More so than any other star pattern, when I see the defining asterism (recognizable star pattern) of Corvus the Crow flying high in the night sky after sunset, I know that it’s spring.

Corvus (KORR-vuss) is the Latin word for crow or raven. Although it’s hard for us to imagine a crow among the sparse scattering of stars in Corvus, we can see in classical star atlases how the ancients imagined the raucous bird: bending over to peck at Hydra the Water Snake, the constellation that winds below Corvus.

Corvus from Johann Bode's 1801 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

Let’s go outside and stretch our wings.

1) About an hour after your local sunset time, face south. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your right shoulder to the west, and you’ll be facing approximately south.

Star maps created with Your Sky

2) You’ll find the constellation of Corvus low in the southern sky, just southwest of the brilliant blue-white star Spica (SPY-kuh) in the constellation Virgo the Maiden. If you don’t know how to locate Spica, read this post.

The five brightest stars in Corvus form the small but distinctive asterism known as the Sail. It looks a bit like the wedge-shaped sail of a Chinese junk, with a bit of mast extending below.

Chinese Junk
Image by Wibean

3) The brightest of the four stars that make up the sail shape is the blue-white giant Gienah. Gienah (JENN-uh) is from the Arabic for wing. Moving counterclockwise around the sail shape, we next come to Algorab. Algorab (ALL-gorr-abb) is from the Arabic for raven. Algorab is a binary system, two stars in orbit around each other, although with the naked eye we see their combined light as one star. Algorab’s component stars are a bright white star and a dim orange one; you should be able to see both with even a modest-sized telescope.

The stars of the Sail asterism in Corvus the Crow

Next in line is the yellow-white giant star Kraz. The meaning of its name is unknown. Finally, where the mast meets the sail is the orange giant Minkar (MINN-kahr), from the Arabic for beak.

Dimmer than the four sail stars, the yellow-white dwarf Alchiba (ull-kibb-AH) marks the bottom of the mast. Alchiba is from the Arabic for tent, a harkening to an earlier Arab tradition that saw the star pattern of Corvus not as a bird but as a tent, important shelter for a desert-dwelling people.

Astronomy Essential: The distance from the Earth to the Sun is about 93 million miles.

Because the Earth’s orbit is elliptical, not circular, its distance from the Sun varies a bit over the course of Earth’s year-long orbit. The average distance, however, is about 93 million miles or 150 million kilometers.

Astronomers use a mathematically calculated constant based on the distance between Earth and Sun and call it one astronomical unit or 1.0 AU. They use this as a unit of measure between objects in our solar system. One astronomical unit works out to be slightly less than the average distance between Earth and Sun; it is equivalent to 92,955,807 miles or 149,597,870 kilometers.

Due to the long distances involved even within our own solar system, expressing distances of objects in miles or kilometers quickly becomes cumbersome, making the AU a compact and useful unit of measurement. We can say, for example, that today Neptune is 29.68 AU’s from Earth. Otherwise, we’d have to say it’s 2,758,928,346.9 miles or 4,440,064,781.6 kilometers from Earth. Either alternative is quite a mouthful.

The Pond

2009-05-28T23:08:00.009-06:00

Last week, we looked at one of my favorite spring star patterns, Three Leaps of the Gazelle. We learned that ancient Arabic star lore holds that the gazelle leapt from a spot in the sky known as the “Pond.” We can view that spot with the naked eye, as it is the well-known Coma Star Cluster in the constellation Coma Berenices (KOH-mah bare-uh-NIGH-seez).

Coma Berenices means Berenice’s Hair. Queen Berenice was a real person, a monarch of ancient Egypt. The Greek legend associated with Her Highness relates that she pledged her hair to the gods if they would keep her husband safe in battle. When he returned in one piece, she cut off her locks as promised and placed them in a temple. By the following day, they had disappeared. The court astronomer— apparently as politically astute as he may have been scientifically minded— determined that they had ascended to the heavens and could be seen as the spangled patch near Leo the Lion’s tail.

Let’s comb the sky for the queen’s tresses.

Star map created with Your Sky

2) Tilt your head back and look at the zenith, the point in the sky that’s directly overhead. Near the zenith, or a bit below it toward the southern horizon, you should spot a fuzzy patch of stars. It will be slightly above and slightly east of Leo the Lion’s tail. This is the Coma Star Cluster (also known by its catalog designation Melotte 111)— what the Greeks saw as a bejeweled head of hair.

This star cluster is the most prominent naked-eye feature of Coma Berenices, and it’s the best way to tell when you’ve navigated into that particular constellation.

3) If you have binoculars or a small, wide-field telescope like the Starblast Astro, examine the cluster a bit more closely. Use your lowest power eyepiece (highest mm number) in your telescope. This is a really big object, so you don’t want to put much magnification on it.

The Coma Star Cluster is an open cluster, a collection of stars that formed around the same time in the same nebula, or cloud of gas and dust. This cluster is believed to have around 40 member stars. You may want to think of them as a sort of family group.

Coma Galaxy Cluster
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Coma Berenices doesn’t really have any other notable star patterns. Its other crowning glory, the Coma Galaxy Cluster, lies hidden to the unaided eye. The dense cluster contains thousands of galaxies, some of which can be observed by an amateur with a large-aperture reflecting telescope.

Astronomy Essential: The planets orbit the Sun at different speeds.

As the planets of our solar system orbit the Sun, they travel at different speeds. The closer the planet’s orbit is to the Sun, the greater its speed. The farther the planet’s orbit from the Sun, the slower its speed. Therefore Mercury, the nearest planet to the Sun, travels at an average orbital speed of 29.7 miles per second, whereas Neptune, the most distant planet, travels at a much slower average orbital speed of 3.3 miles per second.

The acceleration of planets that are closer to the Sun occurs because the closer the planet is, the greater the gravitational force the Sun exerts on it.

The “average orbital speed” is given here because, during its orbit, each planet speeds up when it is nearer the Sun and travels more slowly when it is far from the Sun. This variation in distance from the Sun occurs because the planets travel in elliptical orbits, not perfectly circular ones.

Three Leaps of the Gazelle

2009-05-21T21:51:00.016-06:00

Between two of the boldest naked-eye star patterns in the spring sky lies a third more demure pattern that’s one of my personal favorites. It’s quite easy to spot when you know where to look, so let’s go stargazing, shall we?

1) About an hour after your local sunset time, face west. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west— close enough for our purposes.

2) Tilt your head back and look at the zenith, the point in the sky that’s directly overhead. A little to the north (right), you should spy the distinctive seven-star pattern of the Big Dipper. The Big Dipper is an asterism, a recognizable star pattern, and it lies in the constellation of Ursa Major the Big Bear.

Star maps created with Your Sky

3) Now look a little south (left) and west from the zenith. Look for the Sickle, the curved asterism that marks the head of Leo the Lion. The Sickle looks a bit like its namesake, the old-fashioned farm implement, or like a backwards question mark. Spot it? Great.

4) Look in the space between the curved top of the Sickle and the bottom of the bowl of the Dipper for three pairs of stars widely spaced from one another. Each pair is around the same distance from the other pairs, and the spacing between the two stars of each pair is around the same. In addition, the stars are all around the same magnitude of brightness. This similarity of pattern helps the little pairs to stand out from the stars around them.

These form the asterism known as Three Leaps of the Gazelle. The three star pairs all lie within the constellation of Ursa Major the Big Bear, and they mark three of the bear’s paws.

Ancient Arabic star lore relates that the gazelle was startled by the lash of the lion’s tail when it sprang from “the Pond,” what we know as the Coma Star Cluster in the constellation Coma Berenices (Berenice's Hair). You can spot the Pond naked eye from a dark site; it looks like a large, bright patch just off Leo's tail.

5) Starting at the Pond, the first set of hoofprints you come to are the stars Alula Australis and Alula Borealis. Alula (uh-LOO-luh) is from the Arabic for first leap; Australis and Borealis are Latin for southern and northern, referring to the respective position of each star.

The middle set of hoofprints are the stars Tania Australis and Tania Borealis. Tania (TAH-nih-yuh) is from the Arabic for second leap.

The final set of hoofprints are the ones farthest from the Pond. The northernmost star is Talitha (TAH-lith-uh), from the Arabic for third leap. Its companion has no traditional name, so we know it simply as Kappa, its star catalog designation.

Can you imagine the swift gazelle leaving behind those three pairs of watery hoofprints as it leapt between twin perils of lion and bear?

Astronomy Essential: The Milky Way galaxy belongs to a galaxy group.

The Milky Way, our home galaxy, is a member of a group of galaxies called the Local Group. It contains around 30 galaxies. The two that are closest to the Milky Way are called the Large Magellanic Cloud and the Small Magellanic Cloud. They are much smaller than the Milky Way and can be seen with the naked eye from the Southern Hemisphere.

Another well-known member of our Local Group is the Andromeda Galaxy, which can be seen naked eye from the Northern Hemisphere. The Andromeda Galaxy is the closest large galaxy to our Milky Way; it lies around two and a half million light years from Earth.

Galaxies throughout the universe tend to cluster into groups. The members of these galaxy groups interact gravitationally and sometimes collide.

On Hiatus This Week

2009-05-14T05:44:00.007-06:00

This week I'm off to northern New Mexico to complete my second International Year of Astronomy project, teaching beginning astronomy and observing to the women of Becoming An Outdoors Woman. This is a national organization, and the New Mexico chapter holds their big annual workshop event every May in Raton.

I'm looking forward to seeing a part of New Mexico I haven't visited yet, as well as meeting other outdoor enthusiasts (and prospective stargazing converts).

Until next time, happy star trails to you!

Science v. Poetry

2009-05-07T22:21:00.009-06:00

Recently a fifteen-year-old girl told me she hated science because it was so analytical. Once you break something down into all those little pieces and examine them, she complained, you lose the poetry of the thing.

As someone striving to communicate astronomy and science in a (hopefully) vibrant and accessible way, hearing this stopped me in my tracks. It was all I could do to stammer, "But the little pieces are the poetry!" She seemed not in the least bit convinced.

So I’ve been thinking about this problem a lot lately. How does one convince a creative-minded teenager (she’s in a performing arts school) that science is relevant to her life? Or at least that poetry and science aren’t mutually exclusive? How does one convince anyone of this?

In seeking thoughtful answers to these questions, I must first consider my own science education.

I too was far more drawn to poetry than science when I was growing up. In fact, memorable science experiences are few and far between. I can remember dissecting a frog in a biology class (the icky factor does prevail). I can remember feeling wonder at growing some sort of bacteria in an agar-filled petri dish (probably because it was a hands-on activity). I can remember learning the names of the (then) nine planets in orbital order from the Sun, and seeing a diagram of the concentric planetary orbits.

Everything else–all those science lessons I passively ingested and regurgitated without any real understanding–has been lost.

At home, I would drag a chaise lounge into the middle of my semi-rural backyard at night and find the constellations with the help of my little field guide. But this was hardly a science experience. Other than a twinkling point of light, I hadn’t a clue what a star was. I was initially drawn to stargazing through my love of Greek mythology. Tracing the star patterns was another way to indulge in the romance of those legends. Poetry again.

In my daily orbit, there was no astronomy club, no person with a telescope, no person who’d even seen a telescope. The overt message from teachers was, "Girls do not excel in math and science." In my home, however, there was a love of nature and a reverence for the natural world that has stayed with me, deepened over the years, and fueled my quest for science literacy.

Second, I must consider the current science learning environment in the school the fifteen-year-old attends, a high school in one of the largest cities in the nation. Because it’s an underperforming school, freshmen must take a science course called Integrated Coordinated Science, which covers topics in Earth Science, Physics, Chemistry, and Biology. This ostensibly prepares them for full-blown Physics, Chemistry, and Biology courses over the next three years.

The textbook purports to support an inquiry-based program: the learning of science by asking questions, digging deeper, and inquiring further. This is the current state of the art in science education. I suppose the textbook is better than some. I’ve just never been a big fan of textbooks, and browsing this one didn’t compel me to become one. Although I’m not a trained educator, the curriculum seemed to me to be rather dry and, well, superfluous. Clearly, it wasn't working for the fifteen-year-old. How much science minutiae do students need to absorb if they’re not going to pursue science-related degrees or careers? How many formulaic hoops should they have to jump through?

Yes, I get that there are byproducts of mental discipline and deductive reasoning skill produced in the process of doing the textbook’s prescribed activities and calculations. But wouldn’t it be far more valuable for kids to leave the experience inspired and intrigued, on fire to know more, with a reverence for the scientific approach to life and an understanding that science represents the underpinnings of absolutely everything? To see the intricately beautiful architecture of chemistry and physics when they peel the cover off of anything? To see the light of long-extinct supernovas shining out from their friend’s eyes and imagine the Milky Way spinning like a pinwheel in the vastness of expanding space? To see the poetry in an atom’s electron cloud and a tree’s transpiration of water vapor from its leaves? In short, to fully integrate the truths of scientific knowledge with the poetry of human vision?

This week, go outside and look at the night sky in a new way. See the stars as they are: nuclear reactors transforming hydrogen fuel into helium in their cores, gigantic spinning spheres of unimaginably hot gasses, bubbling cauldrons of light and heat energy. Then imagine them as the swollen, blazing stars of Van Gogh’s masterpiece, Starry Night.

In the battle between science and poetry, we must at least hope for a draw.

Equipped with his five senses, man explores the universe around him and calls the adventure Science. ~Edwin Hubble

Astronomy Essential: We are made of star stuff.

Our bodies are composed of elements forged in the nuclear furnaces of stars.

About three minutes after the Big Bang, the cosmos was a primordial cloud of hydrogen, helium, and lithium. The early generations of stars that formed from this cloud were massive and short-lived. They burned themselves out quickly and ended in cataclysmic explosions called supernovas. These supernovas spread the original three elements, plus additional elements forged in the stars’ nuclear cores, throughout the universe. In addition, more exotic elements that can only form in the extreme conditions of a supernova explosion were created and spewed into the cosmos.

Many of these elements ended up in the nebula (cloud of gas and dust) where our Sun and its attendant planets formed. The life forms that emerged on planet Earth were, therefore, also composed of these elements that came from the stars.

Sporadics

2009-04-30T22:45:00.033-06:00

Last week I witnessed one of the brightest and most colorful meteors (aka "shooting stars") I’ve ever seen. It was the sort that makes you–and everyone around you–whoop like a rowdy fan at a sporting event.

A meteor or shooting star is the streak of light caused by a bit of space dust or debris (meteoroid) burning up as it encounters Earth’s atmosphere. The pyrotechnical display owes less to the size of the meteor than it does to the velocity at which it slams into our atmosphere. In fact, most meteors are merely the size of grains of sand or rice. The real whoppers–known as bolides–that explode and light up the night environment like flashbulbs, might be only the size of peas or pebbles. The occasional big chunk of rock that survives its screaming descent through our atmosphere to impact the ground (or an unfortunate vehicle) is called a meteorite.

I’m accustomed to seeing color in meteors. It’s not untypical to see yellow-colored or green-hued shooting stars, along with run-of-the-mill white ones. Some meteor showers are even known for reliably exhibiting a particular color. The Perseid meteor shower in August, for example, tends to produce meteors with a gold-colored trail.

My recent meteor of note, however, was big, bright, and unexpectedly blue–neon blue. It took my breath away. Color in meteors is caused by both the composition of the meteoroid and the composition of the air it encounters. The blue may have indicated a high magnesium content in the meteoroid.

The blue meteor was most likely a sporadic, a meteor that isn’t associated with a particular meteor shower. A meteor shower is a display that occurs annually around the same time, when the Earth encounters a specific cloud of debris left behind by a comet whose orbit brought it close to the Sun.

To determine if a meteor you spot is a sporadic, first check to see if a meteor shower is occurring. I use the calendar on the American Meteor Society’s website and check the column marked "Activity Period." If there’s no current meteor shower, then chances are any meteors sighted are sporadics.

If, however, you are within a meteor shower’s period of activity, observed meteors may be either part of the shower or sporadics. To determine which, ask yourself two questions:

1) Is the radiant–the spot in the sky from which the meteors of that shower appear to emanate–visible?
The radiant is typically located within the constellation for which the meteor shower is named (e.g., the Lyrids for Lyra and the Perseids for Perseus), and it moves slightly over the course of the shower. A number of websites, such as this one, offer star maps with the radiant location plotted for the duration of the shower.

The radiant may not, in fact, be visible at the time you spot the sporadic because the constellation where the radiant’s located may not yet have risen over the eastern horizon. It’s typical for a meteor shower radiant to rise after midnight, making midnight to morning twilight the best time to view showers. If you see a shooting star before midnight, there’s a good chance it’s a sporadic.

2) If the radiant is above the horizon, can you trace the trajectory of the meteor back to the radiant?
Observe the starting point, ending point, and direction of the meteor observed. Trace the streak of light from the ending point back through the starting point and beyond to see if that path crosses the meteor shower’s constellation of origin. If so, it’s probably associated with the shower. If not, it’s most likely a sporadic.

There are anywhere from two to sixteen sporadic meteors per hour that strike our atmosphere nightly. The farther away from city lights you get, the more shooting stars you’ll see.

As my memorable blue meteor proved, sometimes one random bit of wayward space dust is just as visually exciting as the peak of a major meteor shower.

Astronomy Essential: A comet is a dirty snowball that orbits the Sun.

A comet is a solar system body composed primarily of ice, gas, and dust trapped in the ice, in other words, a dirty snowball. The snowball begins to melt a bit if the comet’s orbit takes it close enough to the Sun. This melting of the ice releases some of the dust, which creates a "tail" of dust streaming out in the comet’s wake. Looking at the dust tail shows us the comet’s path.

A comet has a second tail, which is usually not as easily visible as the dust tail. Electrically charged gas particles streaming from the comet are blown back by the solar wind, a continuous stream of particles given off by the Sun. Therefore, this ion tail, as it is called, always points away from the Sun.

On Hiatus This Week

2009-04-23T21:20:00.004-06:00

This week, I and a few awesome astronomy colleagues are launching our exciting, IYA-inspired project: STAR-HOPPERS Weekend Workshops in Astronomy.

STAR-HOPPERS is a nonprofit program operating in partnership with the University of New Mexico Field Station on the Sevilleta National Wildlife Refuge in central New Mexico, USA.

Until next week, happy star trails to you!

Speed on to Spica

2009-04-16T23:21:00.011-06:00

Last year we learned how to arc to Arcturus using the handle of the Big Dipper. This year, let’s continue along that path and complete a well-known memory prompt for beginning stargazers that bids us “arc to Arcturus and speed on to Spica.”

1) About an hour after sunset, face east. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your back to the west, and you’ll be facing approximately east.

2) Tilt your head back and look at the zenith, the point in the sky that’s directly overhead. A little ways to the left (toward the northern horizon) and just east of the meridian, you’ll find the distinctive seven-star asterism (recognizable star pattern) known as the Big Dipper. The Big Dipper is in the constellation Ursa Major the Big Bear.

Now extend the curve of the Big Dipper’s handle— heading away from the Dipper’s bowl— to the next star along that arc that‘s brighter than the end star of the handle. You’ve arced to Arcturus! Arcturus is the brightest star in the constellation Bootes the Herdsman.

Star maps created with Your Sky

3) To speed on to Spica, simply continue the arc past Arcturus to the next bright star. This is the blue-white dwarf star Spica (SPY-kuh), which is a bit dimmer than Arcturus. Spica lies 260 light years away. A light year is the distance light travels in one Earth year, nearly six trillion miles.

Spica is the brightest star in the constellation Virgo the Maiden. The name Spica comes from the Greek word for ear of grain. The figure of Virgo is associated with the harvest, and she is often depicted carrying an ear of grain.

Virgo in Johann Bode’s 1782 star atlas
Courtesy of Linda Hall Library of Science, Engineering and Technology

The ancient star figure of Virgo is not easily apparent to the modern stargazer. Virgo is one of those constellations characterized by a loose, sprawling collection of nondescript stars with no showy asterisms. If it weren’t for luminous Spica punctuating the arc from Arcturus, most of us would be hard-pressed to locate the dowdy maiden at all.

But now you can arc to Arcturus and speed on to Spica. This is an easy asterism to teach others, and best of all, it covers ports of call in three constellations!

Astronomy Essential: A telescope gathers light; it does not magnify.

The function of any telescope— whether it uses mirrors, lenses, or both— is to gather light and focus it into a clear, bright image.

The eyepiece— the accessory that is inserted into the focuser and through which the observer peers— is the optical element that magnifies the image produced by the telescope. The magnification of the image, or power as it is also called, changes each time a different sized eyepiece is inserted into the telescope.

Shepherd Moon

2009-04-09T23:22:00.016-06:00

Last week, I talked about starting an observing Life List and related how I’d recently checked off two items on my Life List. If you read that post, you know that both items are not for beginners. Rather they’re the elusive companions to a couple of familiar, naked-eye objects that are accessible to beginners.

The first tag-along object I checked off my Life List this year was Sirius B, the dim companion star to Sirius the Dog Star, brightest star in the night sky.

And now for the exciting conclusion…

Tag-along Object #2
On March 28 of this year, I gathered with fellow amateurs in my astronomy club for a much-anticipated Messier Marathon at a dark-sky site. Although I wasn’t “running” the Marathon this year, I was on a scavenger hunt of my own. I’d decided it was a good night to try for that most elusive moon of Saturn: Mimas. Since Saturn’s rings are nearly edge-on right now, it’s an excellent time to scout for the fainter moons. When Saturn’s rings are open, the planet reflects so much more light our way that faint moons get lost in the glare.

Diminutive Mimas (MY-muss) is only 243 miles in diameter—about the distance from Baltimore, Maryland to Norfolk, Virginia. Compare it to Saturn’s largest and brightest moon, Titan, which is 3,200 miles in diameter and which can easily be spotted when viewing Saturn through even a modest telescope. Titan looks like a little star, usually several ring diameters from the planet. If you view Saturn and see only one moon, chances are it’s Titan.

Saturn and the Cassini Division

Source: NASA, ESA and E. Karkoschka (University of Arizona)

Although small, Mimas has a powerhouse purpose. It’s a shepherd moon, so-called because its gravity tugs on the rock and ice particles in Saturn’s rubble-filled rings and herds them into formation. If you observe Saturn with a telescope when its rings are open, you may notice a thin black line inscribed on the surface of the ring plane, circling the planet. This is the Cassini Division, a gap in the rings that yawns nearly 3000 miles wide. The gravitational pull of Mimas is believed to be the force that keeps the Cassini Division clear.

Mimas the shepherd moon and Herschel the "Death Star" crater
Source: NASA

Close up, Mimas would look something like the Death Star from Star Wars, with its surface dominated by a huge impact crater, one third as wide as the moon itself. The crater is called Herschel, after Mimas’s discoverer, the eminent English astronomer William Herschel.

But on that cool spring evening, I was hoping for just a glimpse of a cagey little pinprick of light. Saturn was beckoning with its signature golden light, near the back leg of Leo the Lion. So I started my quest in our observatory dome, looking through a classic, 1950s Cave Astrola 16-inch reflector. The nearly edge-on Saturn looked like an olive on a toothpick.

Star map created with Your Sky

Bill, who was running the observatory that night, found Mimas’s position using the planetarium software on his laptop. A few more seasoned observers (I did tell you in my previous post that you have to be an instigator) climbed the tall ladder and yelled down that they thought they could see it, coming and going as it shimmered on the upper tip of the toothpick. I gave it a try and also thought I could see it dancing on the hairy edge of my vision.

We stumbled down onto the observing field and set upon Geoff, who was visiting from an astronomy club in northern New Mexico, but who had the most aperture on the field: a 24-inch-diameter reflector. Up the ladder to look through his graciously proffered cannon and…yes! There it was, a fleck of light, now separated from the toothpick and forming the bottom point of a diamond of moons. Comparing it to the other three moons in the diamond—Rhea, Dione, and Iapetus— I was shocked by how much dimmer Mimas appeared. It was an exhilarating revelation, because I realized how impossible it would be for me to spot such a faint fleck when Saturn’s rings are open. Sometimes in observational astronomy, timing is everything.

What’s next? Well, I’ve got a late spring/early summer rendezvous planned with astronomer buddy Dave (of Sirius B fame) to hunt down 3C 273 in the constellation Virgo.

3C 273 is the decidedly un-poetic name of the brightest quasar in the night sky. Although it appears dim to us and must be hunted with a telescope/eyepiece of substantial aperture and magnification, 3C 273 is believed to have a luminosity 100 times that of our entire Milky Way galaxy! Discovered in 1963, it was the first quasar found.

Quasars are distant energy sources that emit a tremendous amount of radiation. They are star-like in appearance due to their distance, but quasars are believed to be the bright, energetic cores of galaxies powered by supermassive black holes.

Note that 3C 273 and its quasar brethren are not in the Milky Way. In fact, at around two billion light years away, 3C 273 is considered one of the most distant objects an amateur astronomer can view. I simply can’t resist that challenge.

The quasar 3c 273
Source: NASA and J. Bahcall (IAS)

One final thought on the value of a Life List: there’s nothing to make you feel less like a novice than to find out that fellow observers with a lifetime of observing experience just saw the object on your Life List for the very first time also. Start your Life List…today!

Astronomy Essential: Sunspots are not spots.

Sunspots are irregularly-shaped dark regions on the Sun’s surface caused by intense magnetic activity. Sunspots vary in shape and size, and they’re often larger than the Earth. As the magnetic fields flux, existing sunspots may fade away and new ones may form elsewhere on the Sun.

The magnetic activity in those regions disrupts the flow of heat from the Sun’s core to its surface. Because of this, the sunspots are— although still intensely hot— much cooler than the solar surface that surrounds them.

Sunspots aren’t black either. The contrast in temperature with the blistering hot regions around them simply make them appear very dark in comparison.