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Now That's a Star of a Different Color!

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Week of Feb. 17-23

One thing I've learned from helping stargazers is that beginners often have some deeply-ingrained misconceptions. Many think that the moon can be seen only at night and never in the daytime; others believe that the Big Dipper is always visible in the sky. Still others think we see the stars as they appear now, rather than as they were centuries ago.

But one of the most common misconceptions is this: "If you've seen one star, you've seen 'em all." This is a pretty understandable perspective. After all, stars appear simply as points of light. How different could they possibly be? Well, ask an experienced sky watcher and they'll tell you that no two stars are exactly alike, but that each displays its own personality in a number of ways. One of the most visible of stellar personality traits lies in its color.

Many people don't notice this immediately because the human eye is not capable of perceiving color well under low light conditions. We know this to be true if we've ever looked around a relatively dark room; shapes and shades of gray are easy to spot but colors are virtually nonexistent. Turn the lights on, however, and we find that we're surrounded by vibrant colors.

When gazing skyward at night we discover that star colors — if we can see them at all — are quite subtle. Binoculars or telescopes capture more light than the human eye and make star color a bit more obvious. So if we'd like to see star colors with the naked eye, we need to focus our attention on the brightest of stars.

The best place to start this is within the great constellation of Orion, the hunter. For sky viewers north of the Earth's equator at this time of year, Orion stands majestically midway up in the southern sky after dark. If you're south of the equator, however, it appears midway up in the north.

Orion's large vertical rectangle of four bright stars forms the hunter's shoulders and knees, and at its center lie three stars that form a nearly straight line — the belt of the brawny hunter.

The bright star marking Orion's northeastern corner (the shoulder) is known as Betelgeuse, a word that comes from an Arabic phrase meaning "armpit of the giant." This aging red supergiant star glows with an orange light that is pretty tough to miss. At the opposite corner — in the hunter's knee — lies sparkling Rigel, another supergiant that displays a slightly bluish-white color.

Star colors are more than just a curiosity, they also tell us something about stellar temperatures. While our sun glows with a surface temperature of around 10,000 degrees Fahrenheit, reddish-orange stars like Betelgeuse are relatively cool (6,300 F) and can often live much longer than the sun. Bluish-white stars like Rigel, on the other hand, are tremendously hot (18,000 F). They can only burn this furiously for a relatively short time and, therefore, must be much younger than the sun.

After you've spotted these two fine examples of stellar color, check out some of the other bright stars around the sky to see what you can learn about their relative temperatures and ages.

Visit Dennis Mammana at www.dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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