| December 2003 | |
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This month you should have no problem finding four out of the five visible planets in the night sky, but the famous Big Dipper will be a little tougher to spot. The Big Dipper is famous for pointing stargazers to the North Star, but what do you do when you can't find the Dipper? We say farewell to the constellations of fall, and say hello to bright winter constellations, with a close look at Gemini the Twins. |
 Download this month's star chart! |
In Pursuit of Planets
Mars remains prominent in the evening sky, just south of the Great Square of Pegasus. Saturn is rising early enough to attract attention too. Look for it in the constellation of Gemini the Twins. Between about 3 AM and sunrise, early morning observers may catch Jupiter in the eastern sky near Leo the Lion. The real showcase this month, though, is brilliant Venus, which appears low in the southwest just after sunset. Find a location with a low southwestern horizon, clear of trees, buildings or other obstructions, and you may be able to see Venus for as much as two hours after sunset.
Lost: One Dipper
Many people know that one of the best ways to find the North Star, Polaris, is to look for the Big Dipper. The two stars on the outside of the bowl are known as "the pointers" because drawing a line through them, out of the bowl, shows the way to Polaris and the direction North. However, at this time of year, the Dipper appears very low above the northwestern horizon in the early evening hours. If you live south of 40 degrees north latitude (Nashville is at 36° N) parts of the Dipper actually dip "below" the horizon. Plus, there's no guarantee you'll even have a clear view with buildings, trees, and other obstacles blocking whatever part of the Big Dipper remains above the horizon.
While you could wait until 10 or 11 PM for the entire Dipper to rise above the northeastern horizon, instead look for the bright constellation Cassiopeia, the Queen, which is already visible as the sky gets dark. This constellation is shaped like a lazy letter W. The three central stars of the W form an arrow that points in the direction of Polaris. Consider Cassiopeia to be the "backup plan" for finding north because it is located on the opposite side of Polaris from the Big Dipper. When the Dipper is low on the horizon, Cassiopeia is high in the sky. When Cassiopeia is low in the sky, you can always count on the Dipper to show you the way.
You Say Goodbye; I Say Hello
This month we say farewell to the relatively faint constellations of fall, and greet the bright stars of winter.
Still visible in the early evening is Pegasus, the flying horse. Look for the square that forms the body of the horse low in the west. If you have a dark enough sky, you might be able to catch the star Enif, which marks the nose of the horse. With Enif closer to the horizon than the rest of the horse, it looks as though Pegasus is making a nose-dive right into the western horizon!
Meanwhile in the east, bright winter constellations are rising, with Orion the Hunter at the center of it all. Orion itself is unmistakable, with three stars in a row making up his belt, two shoulder stars, and his two feet. Once you've learned to spot Orion, you can easily begin to spot the other bright stars that surround him. There are few better landmarks in the sky than Orion!
Gemini the Twins
High above Orion in the winter sky is the constellation Gemini. To find Gemini, face south and draw an imaginary line from Rigel in Orion's brighter foot through Betelgeuse in the opposite shoulder up to the two bright stars, Castor and Pollux. These are the brightest close pair of stars seen from the northern hemisphere, and they mark the heads of the twin sons of Zeus.
Play connect the dots with the stars of Gemini and the stick-figure outlines of the twins become apparent. So great was their love for each other that they were, and still are, considered to be inseparable. As Castor sets in the west, Pollux follows immediately. As Castor rises in the east, Pollux is not far behind.
While Castor may appear as a single star to the unaided eye, astronomers have determined that there are actually six stars in the Castor system. It seems that they all formed at the same time from a vast cloud of gas and dust. While some of the stars revolve around each other, there is an even more complex cosmic dance being performed, choreographed by the mutual gravitational forces that hold the entire system together. As such, their orbital periods can last many centuries. It is estimated that 85% of all stars are found in multiple star systems. This makes our Sun more unique - because it's a singleton!
Sharing the Stars
If you are thinking of giving someone the gift of astronomy this holiday season, be sure to check out "Holiday Hazards" to avoid throwing your money into a black hole!