dipper@utastro.UUCP (01/25/86)
One of the brightest stars in the winter sky is Betelgeuse. More on this red star in the constellation Orion -- after this. January 25 Betelgeuse The stars are remote. We can't smell them, touch them, or taste them. But we can learn to know stars because, like people, they're all different. In the southern sky this month, you'll find the red star Betelgeuse. Betelgeuse is one of the most personable of all stars, partly because of its ruddy color and its tendency NOT to twinkle. This melancholy star is located in the well-known constellation Orion. It marks the right shoulder of the hunter. Betelgeuse is red and somber-looking -- but it's one of the brightest stars in the sky. Furthermore, it earns its exceptional brightness because it's intrinsically bright -- not because it's near Earth. Betelgeuse is located some 500 light-years from Earth. To outshine other stars over this great distance, it must be either extremely hot or extremely large. Which is it? Well, you can figure it out yourself if you remember that Betelgeuse is a red star. On Earth, you can heat a piece of metal until it glows first red hot, then white hot. Just as "red hot" is cooler than "white hot" on Earth, so red stars like Betelgeuse are cooler than white stars. Red stars are often old stars. Betelgeuse is old -- it's a red giant star already past its evolutionary prime. Red giants aren't particularly hot, but they are gigantic. The star Betelgeuse is surrounded by a tremendous shell of gas. If Betelgeuse replaced the sun in our solar system, its shell would extend beyond the orbit of Pluto. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin