Hot Star Found
Caption: White dwarfs in the globular cluster M4. In this picture, only the faintest stars are white dwarfs.
Credit: NASA and H. Richer, University of British Columbia

A hot and aging star exhibits something never seen before. Sounds like a lurid Hollywood tale, but the discovery is a cosmic one.

Astronomers have found a white dwarf star with a surface temperature of 359,500 degrees Fahrenheit (200,000 Celsius). It's so hot that "its photosphere exhibits emission lines in the ultraviolet spectrum, a phenomenon that has never been seen before," the researchers said in a statement today.

Ultraviolet light, part of the same electromagnetic spectrum that includes radio waves, visible light and X-rays, is invisible to the human eye.

Stars of intermediate mass, around one to eight times the heft of the sun, terminate their life as an Earth-sized white dwarfs after the exhaustion of their nuclear fuel. During the transition from a nuclear-burning star to the white dwarf stage, a star becomes very hot.

The white dwarf, named KPD 0005+5106, is among the hottest stars ever known. Catching one so hot is a low-probability affair, because they don?t stay that hot for long.

Our sun is about 10,000 degrees Fahrenheit. Scientists have previously theorized that surfaces of the hottest stars could be up to 215,000 degrees F (120,000 degrees Celsius). For short times, when stars much more massive than the sun explode, the inside temperature could reach as high as 10 billion degrees F.

The finding, from observations by NASA's space-based Far-Ultraviolet Spectroscopic Explorer (FUSE), will be detailed in the journal Astronomy & Astrophysics.

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