本帖最后由 gohomeman1 于 2009-11-18 16:55 编辑
http://apod.nasa.gov/apod/ap091117.html
2009 November 17
Dawn Before Nova
Illustration Credit & Copyright: Mark A. Garlick(Space-art.co.uk)
Explanation:
Will this dawn bring another nova?Such dilemmas might be pondered one day by future humans living on a planet orbiting a cataclysmic variablebinary star system. Cataclysmic variables involve gas falling from a large star onto an accretion disk surrounding a massive but compact white dwarf star. Explosive cataclysmic events such as adwarf novacan occur when a clump of gas in the interior of the accretion disk heats up past a certain temperature. At that point, the clump will fall more quickly onto thewhite dwarf and land with a bright flash.Such dwarf novas will not destroy either star, and may occur irregularly on time scales from a few days to tens of years. Although a nova is much less energetic than a supernova, ifrecurrent novas are notviolent enough to expel more gas than is falling in,mass will accumulate onto the white dwarf star until it passes its Chandrasekhar limit. At that point, a foreground cave may provide little protection, as the entire white dwarf star will explode in a tremendous supernova. |
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