dipper@utastro.UUCP (Debbie Byrd) (09/21/85)
Most of the stars that appear bright in our sky really are intrinsically luminous. More on these very bright stars -- after this. September 21 Whales Among the Fishes Many of the stars that appear bright in our night sky are simply close to Earth. They're really very ordinary stars. But some bright stars are brilliant by their nature. In the language of astronomers, they're very luminous, or intrinsically very bright. This kind of bright star is rare in the galaxy. The most luminous stars have been called "the whales among the fishes." But though there aren't many of them, the brightest stars can be seen over hundreds of light-years -- all across this region of the galaxy. It's interesting to think that if any beings exist on planets in our general region of the galaxy, they'd share with us the sight of these same very luminous stars. These stars include some of the most familiar ones in our sky -- Deneb in the constellation Cygnus, both Rigel and Betelguese in Orion, and Antares in the constellation Scorpius. The brightest stars in our sky are sometimes red supergiants -- stars which've have used up their original supply of thermonuclear fuel -- and which have swollen to enormous sizes in the course of burning new fuels. On the other hand, some very luminous stars aren't red -- they're blue. They're young stars born more massive than our sun. They burn their fuel in a rush -- in only a few million years -- but during that time shine like great beacons in this region of the galaxy. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin