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Hubble Finds Possible Evidence for Stellar Theory
By SPACE.com Staff
posted: 03:30 pm ET
13 February 2002
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newborn_pulsar_020213The Hubble Space Telescope has spied a fast-spinning star with an unusual partner. The discovery might just be the missing evidence needed to explain how such quick-spin stars come to be. Of the 90 fast-spin stars known in the universe, (such stars are officially called millisecond pulsars because they spin 'round several hundred times a second) this is the first to be found partnered with a red-hot giant star. All others are paired with small, coolish stars called white dwarfs. The rarity of the super-fast pulsars have piqued scientists interest in their evolution, and their consistent pairing with white dwarfs has been seen as a key. This has led scientists to theorize that the partner stars are involved in kind of "recycling" relationship, where the fast-spinning stars are created when a normal pulsar pulls mass away from a nearby large star. The theory goes that as the normal pulsar sucks up the mass, it speeds-up, becoming a stellar whirling dervish. Conversely, the mass of the contributing star is diminished, and a cool, tiny white dwarf star is left. But pre-dervish pairings have never been seen, leaving a hole in the theory, until now. "Our favored theory [for this observation] is that we are seeing the system before the bloated red star has been emptied of gas and turned into a white dwarf," said astronomer Francesco Ferraro. Ferraro led a team of scientists at the Bologna Astronomical Observatory in Italy. The team conducted several observations of the pulsar-companion system, which resides in the stellar globular cluster NGC 6397, with the aid of the Hubble Space Telescope and the Australian Parkes Observatory radio telescope. The scientists realized their observations were unique when they found a millisecond pulsar partnered to a star whose radius was 100 times greater than a white dwarf, and five times greater than a normal star of similar mass. "We have certainly discovered a very unusual pair," said Ferraro. Still, it may be possible that the companion star is not contributing to the speed of the super quick pulsar. It might just be a normal star that has been captured by the pulsar by chance, said Ferraro. Yet the discovery is the first bit of evidence for the widely held "recycling" idea. More Information: Astronomy News by TopicThis Week in Science & Astronomy: News Briefs
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