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What a gas! First star in a new class.

A novel breed of star, predicted by theory but never before detected, has emerged in telescope observations and satellite data. The young, unnamed object strikes a rare energy balance: While it's hot enough to break up nearby hydrogen molecules, causing them to dissociate into atomic gas, the star lacks the energy to ionize the atomic hydrogen it creates.

Located some 3,200 light-years from Earth in the Milky Way constellation Cassiopeia, the new find represents the first known example of a "dissociating" star. Astronomer Peter E. Dewdney, who took part in the discovery, estimates that several thousand dissociated stars may lie within 6,000 light-years of Earth, hidden from view within thick gas clouds.

At the Dominion Radio Astrophysical Observatoin in Penticton, British Columbia, Dewdney and his colleagues used data from the Infrared Astronomical Satellite to zero in on areas of warm dust - likely settings for starbirth. Later, using a radio telescope, they noticed that some of the dusty zones emitted radio signals at a wavelength of 21 centimeters, a telltale sign of atomic hydrogen. These and subsequent observations, says Dewdney, revealed a star enveloped by several layers of gas.

A thin shell of ionized hydrogen gas lies closet to the star, followed by a thick shroud of atomic hydrogen, as heavy as 1.4 solar masses, all surrounded by a large cloud of molecular hydrogen, says Devdney. He estimates that the star is about 10,000 years old.

Studies of such youthful stars and the interaction of their gas layers can offer new insights into starbirth, Dewdney notes. He and his co-workers at the observatory and the University of British Columbia in Vancouver describe their discovery in the March 20 Astrophysical Journal.
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Title Annotation:hot enough to break up hydrogen molecules but not to ionize them
Author:Cowen, Ron
Publication:Science News
Date:Mar 16, 1991
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