dipper@utastro.UUCP (Debbie Byrd) (06/09/85)
Binary stars orbit around each other. More -- after this. June 9: Stars That Orbit Each Other On today's date in the year 1803, the astronomer William Herschel announced that some stars are binaries -- that is, they orbit around each other. It was already known that some stars APPEAR double. But everyone supposed that the two stars in double systems simply lay near each other along our line of sight. The brighter star was thought to be closer, and the fainter one farther away. No one realized that the two stars could be physically bound together, in the same way planets are bound to our local star, the sun. Still, some astronomers wondered why there were so many double stars. No one knew why until William Herschel found proof of the connection between the two stars in a double system. In his extensive observations of the sky, he noticed that some double stars moved closer together -- or farther apart -- as if they were orbiting around each other. That answer turns out to be true. The vast majority of stars that appear double really are binary systems, consisting of two gravitationally bound stars. It was an important event in the history of science -- the first time anyone showed that gravity works outside the solar system. Today, we know that most stars in the heavens are binaries -- most stars have at least one other star as a companion. What's more, they don't limit themselves to just one! Stars can come in systems of two, three, four -- or more -- and stars in clusters sometimes congregate in numbers as high as a million. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin