dipper@utastro.UUCP (Debbie Byrd) (10/16/84)
An explosion in a distant galaxy showed astronomers that there are such things as SUPERnovae. More on the supernova in Andromeda -- in just a moment. October 16: A Supernova in Andromeda A supernova is a star that explodes. Some past supernovae were so bright that they could be seen in the daytime. Despite estimates that supernovae occur every few decades in our galaxy, there hasn't been one seen in this galaxy for more than 400 years. So astronomers who study supernovae must turn their instruments to other galaxies. History's most famous extragalactic supernova occurred in the Andromeda galaxy. Andromeda is only two million light-years away -- so close that it can be seen with the naked eye as a patch of haze in a dark October night sky. When the supernova known as S Andromedae erupted in 1885, it looked like a strange, fairly bright star that suddenly burst to life in the the hazy patch. In 1885, the prevailing theory on galaxies was that ours was the only one. Scientists at the time believed that S Andromedae lay only a few THOUSAND light-years from Earth and that it was one of the ordinary novae that erupt less violently -- and more frequently -- than supernovae. It wasn't until the 1920's that the cloud patch called Andromeda became known as a separate island of stars, one among billions of galaxies in the universe. Since Andromeda was now known to be MILLIONS of light-years away, astronomers realized that S Andromedae couldn't have appeared so bright from Earth and still be an ordinary nova. It was then that they coined the new name, supernova. Script by Deborah Byrd. (c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin