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Brown Dwarf Survives Jonah Episode With Red Giant
Space Daily US Editor Washington DC (SPX) Aug 03, 2006 Astronomers using ESO's Very Large Telescope have discovered a binary system in which a Jupiter-sized brown dwarf is orbiting an Earth-sized white dwarf. What's unusual about the arrangement, however, is the brown dwarf once actually orbited inside its companion when the white dwarf grew into a red giant. "Such a system must have had a very troubled history," said lead researcher Pierre Maxted of Keele University in England. "Its existence proves that the brown dwarf came out almost unaltered from an episode in which it was swallowed by a red giant." The two objects, separated by only about 250,000 miles, or about Earth's distance from the Moon, complete orbits around each other in only about two hours. The dwarfs were not always so close. Once they were separated by about the same distance as Earth and the Sun. When the star grew into a red giant, its atmosphere stretched out beyond the brown dwarf's orbit, literally swallowing the planet. According to team member Matt Burleigh, of the University of Leicester in England, the brown dwarf survived because its nitrogen atmosphere was dense enough to endure being surrounded by the star's hydrogen envelope. The binary partners did not escape the ordeal unscathed, however. As the brown dwarf spiraled in toward the star's core, "the shock waves generated by this encounter ripped apart the red giant," said lead research Pierre Maxted of Keele University, also in England. Though the brown dwarf survived with its mass intact - about 55 times the mass of Jupiter - it now orbits much more closely to the star and is super-heated, both by direct solar radiation and by tidal energy. According to Einstein's Theory of Relativity, the separation of the two bodies will decrease further over time. Somewhere around 1.4-billion years from now, "the orbital period (of the two bodies) will decrease to slightly more than one hour," said team member Ralf Napiwotzki of England's University of Hertfordshire, who discovered the brown dwarf's existence and its close proximity to the white dwarf using spectral data collected by the VLT. "At that stage, the two objects will be so close that the white dwarf will work as a giant 'vacuum cleaner,' drawing gas off its companion, in a cosmic cannibal act," Napiwotzki said. Related Links ESO VLT PPARC
Dawn Log - Keeping Busy
Pasadena CA (SPX) Aug 03, 2006Dawn continues to keep its human handlers very busy as preparations continue on schedule to meet the planned opening of the launch period on June 20, 2007. Much of June 2006 was devoted to conducting the comprehensive performance tests described in the previous log. |
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