Astronomers discover Universe's hottest white dwarf.Byline: ANI Washington, Dec 13 (ANI): A team of German and American astronomers have discovered the hottest white dwarf in the Universe, using NASA's space-based Far-Ultraviolet Spectroscopic spec·tro·scope n. An instrument for producing and observing spectra. spec  tro·scop Explorer (FUSE).
Known as white dwarf KPD KPD Knoxville Police Department KPD Kommunistiche Partei Deutschlands (Communist Party of Germany) KPD Kokomo Police Department KPD King of Prussia, Pennsylvania (Airport Code) KPD Key Pre-Distribution 0005+5106, it is among the hottest stars ever known with a temperature of 200,000 K at its surface. It is so hot that its photosphere photosphere, luminous, apparently opaque layer of gases that forms the visible surface of the sun or any other star. The photosphere lies between the dense interior gases and the more attenuated gases of the chromosphere. exhibits emission lines in the ultraviolet spectrum, a phenomenon that has never been seen before. These emission features stem from extremely ionized i·on·ize tr. & intr.v. i·on·ized, i·on·iz·ing, i·on·iz·es To convert or be converted totally or partially into ions. i calcium (nine-fold ionized, i.e., CaX), which is the highest ionization stage of a chemical element ever discovered in a photospheric pho·to·sphere n. The visible outer layer of a star, especially of the sun. pho to·spher stellar spectrum.
Stars of intermediate mass (1-8 solar masses) terminate their life as an Earth-sized white dwarf after the exhaustion of their nuclear fuel. During the transition from a nuclear-burning star to the white dwarf stage, the star becomes very hot. Many such objects with surface temperatures around 100,000 Kelvin are known. Theories of stellar evolution predict that the stars can be much hotter. However, the probability of catching them in such an extremely hot state is low, because this phase is rather short-lived. Since its discovery as a faint blue star in 1985, KPD 0005+5106 attracted much attention because optical spectra taken with ground-based telescopes suggested that this white dwarf is very hot. In addition, it belongs to a particular class of rare white dwarfs whose atmospheres are dominated by helium. A detailed analysis of these spectra, combined with ultraviolet observations performed with the Hubble Space Telescope Hubble Space Telescope (HST), the first large optical orbiting observatory. Built from 1978 to 1990 at a cost of $1.5 billion, the HST (named for astronomer E. P. Hubble) was expected to provide the clearest view yet obtained of the universe. (HST), had led to the conclusion that KPD 0005+5106 has a temperature of 120,000 Kelvin, which made it the hottest member of its class. Although theory predicted the existence of such hot white dwarfs, the star nevertheless represents a challenge to the concepts of stellar evolution because of its composition. The measured calcium abundance (1-10 times the solar value) in combination with the helium-rich nature of its atmosphere represents a chemical surface composition that is not predicted by stellar evolution models. (ANI) Copyright 2008 Asian News International The Asian News International (ANI) agency provides multimedia news to China and 50 bureaus in India. It covers virtually all of South Asia since its foundation and presently claims, on its official website, to be the leading South Asia-wide news agency. (ANI) - All Rights Reserved. Provided by Syndigate.info an Albawaba.com company |
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