Thursday, December 9, 2010

Jumpin' Geminids!

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.

Thursday, November 25, 2010

Honk If You Love the Heliosphere

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.

Thursday, November 11, 2010

How Far Can We See? (part two)

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!

Thursday, November 4, 2010

How Far Can We See? (part one)

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.

Thursday, October 21, 2010

Opposition - It's a Good Thing

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.

Thursday, September 23, 2010

The Kids Are Far Out - part three

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?

Thursday, September 16, 2010

The Kids Are Far Out - part two

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.


Thursday, September 9, 2010

The Kids Are Far Out - part one

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.

Thursday, September 2, 2010

Why Is the Moon So Bright?

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?

Thursday, August 26, 2010

Dear Mr. Horkheimer

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.







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.

Thursday, July 15, 2010

Fire and Ice

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.

Thursday, June 24, 2010

Diamond of Virgo

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.

Thursday, May 27, 2010

The Sickle

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.

Thursday, May 13, 2010

Cup of Stars

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!

Thursday, April 29, 2010

Carpe Cosmos

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.

Thursday, April 15, 2010

Seeing Double

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.




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, 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.




Thursday, April 1, 2010

Tripping the Light Fantastic - Part 2

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.

Thursday, March 25, 2010

Tripping the Light Fantastic - Part 1

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.

Thursday, March 11, 2010

Delusions of Grandeur

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.

Thursday, March 4, 2010

Deep-Sky Diving

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.

Thursday, February 11, 2010

We Are Family

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.

Thursday, January 28, 2010

Chill Out

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.

Thursday, January 21, 2010

That's Hot

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!

Thursday, January 14, 2010

Where Does Space Begin?

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.

Thursday, January 7, 2010

Index of Posts 2007-2009

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