dipper@utastro.UUCP (Debbie Byrd) (11/05/84)
Two white dwarf stars in orbit around each other could someday explode as a supernova. More on binary white dwarfs -- right after this. November 5 Binary White Dwarfs Binary stars are two stars in orbit around each other. Such systems are common in the galaxy. But astronomers have been looking for a special kind of binary star -- a system in which both stars are white dwarfs. A white dwarf star is a star in a final stage of its evolution. Unlike our sun and many other stars, a white dwarf no longer produces energy through the process of thermonuclear fusion -- because all its thermonuclear fuel has long since been used up. A white dwarf star is a small, very dense object -- perhaps the size of the Earth -- that's held up by the incredible pressure of electrons stripped from atoms. Theories predict that double star systems should exist where both stars are white dwarfs. Astronomers have looked for binary white dwarfs. One sure candidate is the the star system G61-29 -- visible only through large telescopes -- but now in the sky before dawn. White dwarfs in double star systems may be what cause certain kinds of supernovae. A supernova is a star that vastly increases in brightness -- in fact, one supernova can briefly outshine an entire galaxy of stars. It's thought that binary white dwarf stars gradually get closer together in orbit. Eventually the heavier star begins to pull matter off of the lighter one. After enough of its companion has been eaten, the first star can become unstable, causing a gigantic explosion -- a supernova! Astronomers who search for binary white dwarfs hope to gather evidence to find out whether this theory is true. Script by Deborah Byrd. (c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin