Asri-unix.1268 net.space utzoo!decvax!cca!mclure@SRI-UNIX@sri-unix Wed Apr 21 02:35:22 1982 Eta Carinae !a034 0159 21 Apr 82 PM-Super Star,550 Star Explosion May Be Visible During Daytimer new grafs and SUBS By WARREN E. LEARY AP Science Writer WASHINGTON (AP) - A stellar event of the highest magnitude is imminent, say astronomers, who are predicting that the largest star in the Milky Way could at any moment become the next supernova observable from Earth. The rare phenomenon, signalling a massive explosion of the giant, swollen star, could be sighted at any time - today or 10,000 years from now - but astronomers say it will be ''soon'' in the cosmic scale of time. When it does, the star will suddenly appear to be up to 100 million times brighter than before it exploded and could be seen even in broad daylight for a time. Dr. Kris Davidson of the University of Minnesota in Minneapolis said Tuesday that the star Eta Carinae appears to be the most likely candidate in our part of the Milky Way galaxy to become a supernova. ''It may not be the next, but we can't identify another one that will go off in the next 100,000 years,'' Davidson said in a telephone interview. Scientists estimate that a supernova occurs every 50 years among the billions of stars in our galaxy. But because only about a tenth of the galaxy is visible from the Earth, one can be observed only every couple of hundred years. The last supernova recorded occurred in 1604, however, so another is long overdue. Eta Carinae, visible only from the Southern Hemisphere, appears to be the only star of its kind discovered in the Milky Way. It is 100 times more massive than the sun and has a diameter of about 60 million miles, compared with less than a million miles for the sun. ''We call it a blue super giant and it really is unique,'' Davidson said. ''There are some stars in other galaxies that look similar, and these are among the most luminous stars there are.'' Such a star has a typical lifetime of only 2 or 3 million years, compared with several billion years for a slower-burning body such as the sun. The giant stars are so bright because they burn up their hydrogen fuel at a tremendously accelerated rate, astronomers say. Stars become supernovas when they burn up most of their fuel, swell and then explode in a burst of light and energy. The explosion of Eta Carinae would cause it to give off more light than the combined brilliance of all the other stars for a period of weeks, Davidson said. It would be visible from Earth as a bright point of light even in the daytime. Eta Carinae is about 9,000 light years from Earth. A light year is the distance light travels in space in a year at 186,000 miles per second, about six trillion miles. That means its explosion into a supernova actually may have occurred thousands of years ago but hasn't yet become visible here. The star has been known to astronomers for hundreds of years. But because a thick mass of dust and gas it previously ejected obscures direct observation, no one knew whether it was a new star forming or an old star dying. Davidson and Drs . Nolan R. Walborn and Theodore R. Gull of the Goddard Space Flight Center in Maryland made new observations using the Cerro Tololo Inter-American Observatory in Chile and the International Ultraviolet Explorer Satellite orbiting the Earth. Their work, financed by the National Science Foundation and published in the current Astrophysical Journal, determined that the star is nearing the end of its life. ap-ny-04-21 0459EST ********** ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.