Three astronomers have discovered a star many times brighter than the sun -- perhaps the most massive and luminous star known to mankind -- in a companion galaxy of our own. The professors at the University of Wisconsin-Madison, who found the "super-massive" star in the Tarantula Nebula, names it R136a and said it may release 150 million times as much energy as the sun. Joseph P. Cassinelli, John S. Mathis and Blair D. Savage announce the discovery at a recent meeting of the American Astrological Society in Albuquerque. Cassinelli said R136a has a mass 3,500 times that of the sun and a radius 120 times that of the sun. Its surface temperature is about 60,000 degrees centigrade, 10 times that of the sun, he said. He said it is losing atoms at a rapid rate and has an estimated lifespan of a million years, compared to the sun's lifespan of 10 billion years. The Tarantula Nebula is a cloud of ionozed hydrogen gas in the Large Magellanic Cloudf, a small galaxy visible from the southern hemisphere as a companion to our Milky Way. Cassinelli said the star apparently gets its energy by converting hydrogen to helium, like the sun. The three looked at the nebula's center with the International Ultraviolet Explorer satellite and saw two possbililities: There are 40 giant blue stars within a volume just over a light year across, an incredible idea considering most stars are much fainter and much farther apart. Or, there is a single "super-super-giant star," an equally incredible thought, if it were not for supporting data and theoretical calculations which match that data. "It's just the right luminosity to account for the extreme brightness of the nebula," Cassinelli said. He said the theoretical speed of the wind from such a star and the star's high temperature match the observation.