Thursday, March 26, 2009

Naked-Eye Marathon

On Saturday, March 28, at 8:30 p.m. local time (wherever you live), you are invited by the Earth Hour organizers to turn off all your (non-essential) lights for one hour. In addition to the global energy savings and the sociopolitical statement about saving the planet, there’s a less heralded benefit to be derived from this action: a darker environment for stargazing!

If your neighborhood is a darker place during Earth Hour, why not run a marathon— around the sky with your eyes? On that evening, many amateur astronomers will be doing just that, since New Moon weekends in March and April are prime times for the Messier Marathon.

The Messier Marathon (pronounced MESS-ee-yay) is part celestial scavenger hunt, part athletic endurance event. During a Marathon, amateurs attempt to observe all 110 objects in the Messier catalog in one night, using binoculars and telescopes. The catalog is the compilation of the famed 18th century French astronomer Charles Messier, and it has become a staple of amateur astronomy. Because of where the Messier objects are located in the sky, the Marathon is only do-able in March and April. It’s an all-night affair, as some objects must be grabbed right after sunset and some right before sunrise.

Amateur astronomers prepare for a Messier Marathon

What I propose for Earth Hour is not so daunting. Instead, I invite you to try to spot as many of the naked-eye items on the following list you can. No equipment required, except of course your eyeballs. If Earth Hour is clouded over at your location, try it another evening this week. Give yourself one hour only. Don’t forget to dark adapt.

Start by facing 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. If you face it, to your back will be east, to your right will be north, and to your left will be south.

To print out a star map for March to aid you in your scavenger hunt, visit Sky Maps. Good luck!

1) The crescent Moon
If you have an obstructed view of the western horizon, look WNW just over the horizon and try to spot the seven-percent-illuminated waxing (growing) crescent.

2) Pleiades
Above the Moon, about two fist-widths away, is the fuzzy patch also known as the Seven Sisters. This star cluster has been known since antiquity.

3) Hyades and the Bull’s Eye
Left, or south, of the Pleiades are the V-shaped star cluster of the Hyades and the brilliant reddish star Aldebaran, which marks the eye of Taurus the Bull.

4) Hourglass of Orion and Orion’s Belt
Continuing south, you come to the Hourglass asterism (recognizable star pattern) of Orion the Hunter. Look for the diagonal three-star pattern that cinches the hourglass. This is Orion’s Belt.

5) Sword of Orion and Orion Nebula
Dangling from Orion’s Belt is a three-star pattern called the Sword of Orion. Look at the middle “star” and you’ll actually be looking at a stellar nursery, a star-forming nebula 20,000 times the size of our solar system! It looks like a star with the naked eye because of its distance.

6) Segment
Starting again at the Pleiades, go right or north to reach the curved six-star asterism that forms the “backbone” of the constellation Perseus. It is known as the Segment.

7) Lazy W
Continue north from the Segment to reach the distinctive W-shaped asterism of Cassiopeia the Queen.

8) Pentagon and the Kids
Continuing above, or east of, the Pleiades, look for the Pentagon asterism of Auriga the Charioteer. Just under Capella, the brightest star in the Pentagon, is a small triangle of stars. This is the asterism known as the Kids.

9) Dog Star
Now face south. Below and to the left of the Hourglass of Orion is the brightest star in the night sky, as seen from Earth. This is Sirius, also known as the Dog Star. It is in the constellation Canis Major the Big Dog.

10) Winter Triangle
Draw a line between Betelgeuse, the brilliant red star at the upper left of the Hourglass and Sirius the Dog Star. Now look for the third point of the equilateral triangle northeast of Sirius. This is the star Procyon in the constellation Canis Minor the Little Dog.

11) Twins
Continuing north from Procyon about the width of two fists, you’ll come to two bright stars that are close together. These are Castor and Pollux, the Gemini Twins. Pollux is the brighter of the two.

12) Beehive
Triangulate eastward from Pollux and Procyon and look for a fuzzy patch. This is the famous Beehive, a star cluster in the constellation Cancer the Crab. It is also known as Messier 44 or M44.

13) Sickle and the Lion’s Heart
Continuing east from the Beehive, look for an asterism shaped like a backwards question mark. This is the Sickle, or the head of Leo the Lion. The bright star at the bottom of the question mark is Regulus, the star that marks the Lion’s heart.

14) Saturn
Now face east. Below Regulus is a bright golden “star.” This is the ringed planet Saturn, one of five planets that can be seen with the naked eye.

15) Spica
Continuing below Saturn in an eastward direction, look for a very bright star low over the horizon. This is Spica, 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 is often depicted carrying an ear of grain.

16) Berenice’s Hair
To the left and a bit below (northeast of) Saturn, look for a large spangly patch. This is the star cluster known as Berenice’s Hair or the Coma Star Cluster. It has been known since antiquity.

17) Big Dipper
Now face north. Look east of the meridian for the distinctive seven-star asterism known as the Big Dipper. It lies in the constellation of Ursa Major the Big Bear. It will be upside down, pouring its contents toward the northern horizon.

18) Arcturus
Follow the curving handle of the Big Dipper eastward to the next bright star. This is orange Arcturus. It name means guardian of the bear, as it appears to follow Ursa Major around the sky.

19) Horse and Rider
Look closely at the middle star in the three-star handle of the Big Dipper. If you have good eyesight, you should see two stars. Bright Mizar and dim Alcor are reported to have been used by the Romans and the Arabs as a vision test. This pair is commonly known as the Horse and Rider.

20) North Star and true north
Draw an imaginary line between the two end stars in the Big Dipper’s bowl--the ones that are farthest from the handle end. These are known as the “Pointer Stars,“ because they point the way to the North Star. Extend that line about five times its length. The first fairly bright star you come to is Polaris, the North Star. It’s slightly dimmer than the end pointer star.

Beginning stargazers are often surprised to learn that the North Star isn’t one of the brightest stars in the sky. Its importance to us is its location, not its magnitude of brightness. Now that you’ve found Polaris, face it square and you will be facing geographic north, also known as true north.

Astronomy Essential: The Sun does not rise or set.

Say what? That’s right, you heard me. The ancient, Earth-centered concepts of sunrise and sunset are cemented into our language. But the Sun doesn’t actually rise or set, except in an Earth-centered universe. And we are modern people and therefore know that the Earth is not the center of the universe.

We do know, however, that the Earth spins on its axis 24/7. We spin toward the east, and so the Sun appears to “rise” over our eastern horizon and “set” on our western horizon. The Sun’s apparent motion, or the way it appears to move in our sky, is from east to west. However, in the Sun-Earth system, it is planet Earth that is moving, not the Sun.

Thursday, March 19, 2009

Ain't We Got Fun

Every morning
Every evening
Ain't we got fun…

Every eight years, planet Venus is positioned such that we Northern Hemisphere dwellers can see it at both dawn and dusk— on the same day! That time has come.

On March 22nd, 23rd, and 24th, you will have a chance to see Venus as both Morning Star and Evening Star.

To observe this phenomenon, pick an observing location with unobstructed views of the eastern and western horizons. In the morning, shortly before sunrise, look ENE for the brilliant planet, low over the horizon. It will be north of where the Sun rises. Do not look directly at the Sun after it rises, as this will damage your eyes!

In the evening, just after sunset, look WNW for the goddess of love, low over the horizon and north of where the Sun sets.

Start looking on the 22nd, just in case clouds or foul weather eliminate your view at either dawn or dusk. The goal here is to see Venus twice in one day.

Venus in crescent phase (NASA)

If you have binoculars or a telescope, and you’re careful to catch Venus before the Sun rises or after it sets, look for the ultra-thin crescent phase that Venus is currently exhibiting. You can also look for the cusp extensions that may be visible; sunlight scattered by Venus’s atmosphere makes the ends of the thin crescent appear to stretch more than halfway around the limb (outer edge) of the planet’s disk!

If you’re successful with your double observation, post a comment here and claim your bragging rights!

Night or day-time
It's all play-time
Ain't we got fun?

Astronomy Essential: All solar system bodies except the Sun shine by reflected light.

Earth, our Moon, the other planets and their moons, the asteroids, and the comets of our solar system appear illuminated because they reflect sunlight, not because they are producing light. However, stars— of which our Sun is one— are themselves light sources.

Reflection is the rebounding of light from a surface.

Thursday, March 12, 2009

Cloudy Plan

It happens to each of us sooner or later. Our stargazing plans are thwarted by clouds.

It doesn’t matter how much time or thought you put into creating your observing list for the evening, how lovingly you cleaned your binoculars and eyepieces in preparation, or how long you dark adapted. Sometimes, the sky gods are simply not smiling.

Those of us who design and deliver night-sky education programs learn pretty quickly that we always have to have a “cloudy plan.” A cloudy plan is the set of indoor activities you roll out in a hurry when the weather goes south and there isn’t a sucker hole in sight.

What’s your cloudy plan? When the promise of deep-space photons doing the can-can on your retinas is heartlessly revoked by foul weather, how will you drown your sorrows? With a carton of fudge ripple ice cream? With a marathon of Trick My Truck episodes? Or…might I suggest an alternative?

When the cosmos rains on my parade, I simply boot up my computer and head out into cyberspace (well, OK, after I kick my rocker box and set my observing list on fire in the gas grill). With the cornucopia of astronomy websites now available on the internet, I can usually find just the right pick-me-up for my dejected eyeballs.

Here are my lucky-seven picks for cosmic-eye-candy websites on which to while away a cloudy night. If there is an antidote for what ails you, you might just find it here.

1) Astronomy Picture of the Day
I don’t know about you, but I regularly break my resolution to visit this site daily. So I’m always playing catch up via the "Archive" link. On a cloudy night, this can be a good thing, as I can saturate my rods and cones with a dazzling variety from “the largest collection of annotated astronomical images on the internet.” The image captions are highly readable for non-scientists and peppered with hot links to other web pages for deeper reading.

Orion Nebula: a star factory in the Milky Way
Source: ESO

2) ESO Image Gallery
Supported by 14 European countries, the European Southern Observatory (ESO) comprises several telescopes in Chile, one of the premiere locales on Earth for ground-based astronomy. Choose images from such categories as solar system, stars, star clusters, nebulae, galaxies, and galaxy clusters. Try more exotic fare from categories like quasars and black holes, and cosmology. Click on each thumbnail image for a larger image with accompanying explanatory text.

Solar prominence (eruption) on our Sun
Source: SOHO (ESA & NASA)

3) SOHO Image Gallery - Best of SOHO
An amazing, astounding, and awe-inspiring collection of images of our nearest star, the Sun. The images were captured by the space-based Solar & Heliospheric Observatory (SOHO). Each thumbnail click reveals a brief caption and a choice of viewing the image at several resolutions.

You’ll never look at El Sol quite the same way again.

4) Spitzer Space Telescope Image Gallery
This space-based observatory enables us to see celestial objects in a new way— in the infrared spectrum, outside the narrow band of visible light we humans operate within. Choose from categories such as galaxies & the universe, other Milky Way objects, and protoplanetary & debris disks.

Tycho’s Supernova Remnant in the Milky Way
Source: Chandra and Spitzer Telescopes
Credit: X-ray: NASA/CXC/SAO, Infrared: NASA/JPL-Caltech; Optical: MPIA, Calar Alto, O.Krause et al.

5) Chandra X-Ray Observatory Photo Album
Through the oeuvre of this space-based observatory, we can again venture outside our comfort zone of visible light into the mysterious X-ray universe. There are no thumbnails, so to view images, you’ll select individual files grouped under category headings.

The Northern Lights
Copyright 1995-2003 Jan Curtis

6) The Aurora Page by Jan Curtis
For a change of pace, let’s move a little closer to home and wander through this spectacular gallery of aurora images shot in Alaska. Auroras, also known in the Northern Hemisphere as the Northern Lights, are colorful sky displays that occur primarily in polar regions when particles from the solar wind slam into Earth’s atmosphere and excite the gasses there.

The star-packed heart of the Milky Way
Credit: NASA and The Hubble Heritage Team (STScI/AURA)

Acknowledgment: J. Trauger (Jet Propulsion Laboratory)

7) Hubble Heritage Image Gallery
No survey of premium cosmic-eye-candy sites would be complete without a trip to the “Oracle,” aka the Hubble Space Telescope site. This prolific space-based observatory has revolutionized astronomy world-wide— not just for professional scientists but for every man, woman, and child on the planet.

The mission of the Hubble Heritage Project is to emphasize particularly compelling Hubble images and, in doing so, to build a bridge between the endeavors of scientists and the general public.

On the website, you’ll select images from a sea of thumbnails grouped under object types and Hubble instruments. Once each image has loaded, choose “Caption” or “Fast Facts” from the menu for, respectively, a full-length text explanation or a bare-bones data sheet that includes object name, constellation, distance, and dimensions.

Do you have a favorite cosmic-eye-candy site you like to savor on cloud-bound nights? By all means, post a comment and share it with us.

And bon appetit!

Astronomy Essential: The reason for the seasons is Earth’s tilted axis.

It’s a common misconception among the peoples of the world that the Earth’s proximity to the Sun determines our seasons. Not so. In fact, here in the Northern Hemisphere, we’re closer to the Sun when it’s coldest— in winter!

Earth’s tilted axis is the real culprit. The axis is the imaginary straight line that connects the North and South Poles and around which the Earth turns. Instead of sitting upright in the saddle as we gallop around the Sun, our axis “slouches” a bit— listing 23.5 degrees. When it’s tilted toward the Sun, more direct sunlight falls on the Northern Hemisphere; we call this “summer.” At the opposite end of our orbit, when the axis is tilted away from the Sun, we receive less direct sunlight and it’s “winter.”

To think about this another way, consider how much higher in our sky the Sun appears to be in the summer versus the winter. Since we’re tilted towards it in the summer, it’s over our heads, blazing down on us. And since we’re essentially leaning back away from it in the winter, it hangs low in our sky with sunlight hitting us weakly, at a narrowly acute angle.

Thursday, March 5, 2009

Perseus the Hero

The constellation Perseus is— along with Andromeda, Cassiopeia, and Cepheus— a member of the star groupings known collectively as the Royal Family. The four royals featured prominently in Greek mythology and have been immortalized in the heavens above.

Perseus, Cassiopeia, and Cepheus all lie along the band of the Winter Milky Way, and if you’re observing from a dark site, you can use this knowledge to aid you in locating our hero.

1) Wait at least one hour after sunset to begin observing, so your sky is good and dark.

2) 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

3) First locate the Lazy W asterism (recognizable star pattern) of Cassiopeia, west of the meridian. It will be inverted, so it will look more like an “M.” Below it, toward the northern horizon is the House asterism of Cepheus. If you can see the glowing band of the Winter Milky Way stretching up from the northern horizon behind Cepheus and Cassiopeia, follow it along to the next group of bright stars. This is Perseus.

4) If you can’t see the Milky Way, draw an imaginary line between the middle star of the Cassiopeia “M” and the star to its right, or south. Continue extending the line south, and the next bright group of stars you come to is the “backbone” of the constellation Perseus, the asterism known as the Segment.

This curved string of six naked-eye stars is quite prominent, and if you were to extend the curve beyond the last star, you would come to blazing Capella, the brightest star in Auriga the Charioteer.

5) The brightest star in the Segment— and in Perseus— is Mirfak (MURR-fahk). Mirfak is Arabic for the elbow of the Pleiades. I can’t help but imagine the daughters of Atlas breaking with decorum and giving Perseus a sharp elbow to the ribs.

Mirfak is a yellow-white supergiant star, and the brightest member of a young open cluster of stars. An open cluster is a loose group of stars that formed around the same time in the same nebula (cloud of gas and dust). You can see the brighter stars of the cluster surrounding Mirfak with your naked eye, but binoculars or a telescope will reveal a gorgeous collection of stars.

6) The second brightest star in Perseus is the notorious variable star Algol, aka the Demon Star. Algol (AL-goll) is Arabic for the demon’s head. Algol is variable because it is a double star, and its orbiting companion star eclipses it like clockwork every 2.8 days. This makes Algol’s brightness dip suddenly and dramatically.

Perhaps this eerie “winking out” effect is what led a number of cultures to associate this star with death, violence, and danger. The ancient Greeks considered Algol the decapitated head of Medusa, being brandished by her slayer, Perseus. Medusa was the snake-haired creature whose frightful appearance turned anyone who looked upon her to stone.

Look for Algol southwest of Mirfak.

7) At the end of a string of five stars that meanders south from Mirfak is the star Atik. Atik (AH-tick) is Arabic for collarbone of the Pleiades. Atik is a blue-white giant star that is dimmed considerably to our view by interstellar dust in the Milky Way.

8) Go back up the five-star string two places to locate the only other star in Perseus with a traditional name: Menkib. Menkib (MENN-kibb) is Arabic for shoulder of the Pleiades. These references to the Pleiades in the star names of Perseus recall a larger Arabic constellation that encompassed the Pleiades and certain stars in Perseus and Cassiopeia.

Menkib is a blue giant star, 40 times more massive than our Sun. Menkib is destined to end its life in a cataclysmic explosion known as a supernova.

Astronomy Essential: Most of the mass of the solar system is the Sun.

To be more specific, the Sun contains 99.8 percent of the mass (quantity of matter) of the solar system. That’s right, the planets, moons, asteroids, comets, and interplanetary dust represent just two-tenths of a percent of the mass of the entire solar system!

To help you picture the scale involved, imagine a bowling ball. This is the Sun. Now imagine a single peppercorn placed next to the bowling ball. This is the Earth.

The Sun rules. Any questions?