dipper@utastro.UUCP (01/26/86)
The most massive stars burn hottest and brightest -- but they live a relatively short time. More on one such star -- after this. January 26 Rigel Yesterday we talked about Betelgeuse, a bright red star in the constellation Orion. But Betelgeuse isn't the brightest star in Oron. That distinction goes to Rigel, a pure white star that marks the hunter's left foot. Orion is the only constellation in the sky with two such brilliant stars as Betelgeuse and Rigel. Both stars are bright and very distant from Earth -- but the similarity ends there. Although Betelgeuse is bright because it's huge, it's a relatively cool star. Rigel is smaller -- but it's one of the hottest stars in the sky. Rigel radiates more light than any other visible star -- 150 thousand times more than the sun! Its tremendous energy production is a clue that Rigel is a much younger star than either Betelgeuse or the sun. The hottest stars are those born with the greatest amount of mass. Unlike their less massive brothers, stars like Rigel expend all their fuel in a great rush and so can last only a few million years. If Rigel had been born when the sun was -- billions of years ago -- it would have long since burned itself out. So we know Rigel is a relatively young star. As stars like Rigel age, they go through dramatic changes in structure. Someday, when Rigel exhausts its fuel supply, it'll lose its white-hot color. It's outer layers will expand, and, as they do, they'll cool. Rigel will then become a red giant star -- much like Betelgeuse, its neighbor in the sky. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin