dipper@utastro.UUCP (Debbie Byrd) (10/28/86)
Why Jupiter is sometimes described as a star that didn't make it -- after this. October 28 Why Jupiter is a Planet The planet Jupiter is now very easy to see. It's that bright object high in the east when night begins. Last month, Jupiter was passed by Earth in the race around the sun. Now it's still a brilliant beacon in our skies -- still brighter than any star -- and very conspicuous every evening. Look outside tonight -- and you can't miss seeing the largest planet. Again, it's the bright object high in the east after the sun goes down. Jupiter is the largest planet in our solar system. Eleven Earths could fit side by side in front of it. It's so massive that, on some great cosmic scale, it would outweigh all the other planets combined. In fact, Jupiter came closest of all the planets to becoming a second sun. Stars like the sun require at least a certain amount of mass to turn on -- to begin fusion reactions in their cores -- the reactions which enable them to shine. If Jupiter had been born with about a hundred times more mass it would have become a second sun -- sometimes faintly illuminating our nights -- sometimes making our daytime a little brighter. As it was, Jupiter was born too puny to become a star. But it still radiates some energy from its interior -- through a contraction and cooling-down process begun at the birth of the solar system. Jupiter radiates about twice as much energy as it absorbs from the sun -- energy that in the past dramatically affected the rest of the jovian environment. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin