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.