dipper@utastro.UUCP (Debbie Byrd) (11/02/84)
There's a star about the size of our planet Earth, visible through small telescopes at this time of year. More on Van Maanen's Star -- right after this. November 2 Van Maanen's Star Our sun is about as wide in diameter as one hundred planet Earths. Some stars are much bigger yet -- and then again some stars are very small. In the November evening sky, there's a star visible through small telescopes that's about the same size as the Earth. This star is called Van Maanen's Star for the astronomer who called attention to it in the year 1917. Van Maanen's Star is what's known as a white dwarf. Long ago it used up the hydrogen and helium needed to make the star shine -- or produce energy -- through the process of thermonuclear fusion. With no vast continuous release of heat in its interior, the star's own gravity compressed it down to a far smaller size -- where electrons stripped from atoms keep the star from collapsing further. Van Maanen's Star contains about the same amount of total matter as our sun. But it's only about the size of planet Earth, so its density is far greater -- about twenty tons to the cubic inch -- or nearly one million times the density of water. There are many white dwarf stars in the galaxy -- but this is one of the closest at about 14 light-years away. Van Maanen's Star is presumably much older than our sun, since it's had time to stop producing energy and begin cooling off. It will now spend aeons slowly cooling until it reaches the cold, dark "black dwarf" stage -- a fate lying in wait for nearly all stars -- and due to overtake Van Maanen's Star billions of years from now. Script by Deborah Byrd. (c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin