benson 2009-3-25 11:59
復發新星蛇夫座RS星
Recurrent Nova RS Ophiuci
[img]http://i5.tinypic.com/4ct5rtw.jpg[/img]
影像版權與提供: John Chumack
[color=navy]Explanation: [/color]
[color=dimgray]This pretty star field in the constellation Ophiucus is centered on a star not often seen - RS Ophiuci. In fact, early last week RS Oph suddenly became visible to the naked eye for the first time since 1985. A type of cataclysmic variable star classified as a recurrent nova, RS Oph dramatically increased in brightness from 11th magnitude, too faint to appear on some star charts. Historically, RS Oph was seen to go through only four similar outbursts since 1898. Such stars are now modeled as interacting binary star systems, composed of a compact white dwarf star co-orbiting with a swollen red giant. As material falls away from the red giant it collects in a rotating accretion disk before ultimately falling on to the white dwarf. Disk instabilities, or a build up of material on the compact star result in the occasional but rapid release of energy through nuclear burning. At an estimated distance of 3,000 light-years, RS Ophiuci is now reported to be fading rapidly. This telescopic view spans about 2 degrees (4 full moons) and was captured on the morning of February 16 from the RAS Observatory under New Mexico skies. [/color]
[color=navy]說明:[/color]
[color=dimgray]這片位在 蛇夫座(Ophiucus) 的美麗星野，視野的中心在通常不可見的蛇夫座RS星 (RS Ophiuci)。上個星期 蛇夫座RS星突然 變亮，從有些星圖也不編列的11星等恆星，變得自1985年以來首次肉眼可見。蛇夫座RS星被歸類為激變星之一種的 復發新星，它自1898年以來，只經歷過四次類似的 爆發。這類變星現在被認為是種作用雙星系統，內有一個緻密的白矮星和一個和它互相繞行的膨脹紅巨星。在蛇夫座RS系統內，物質由巨行星飛出，聚集成緻密天體周圍的拱星盤，最後才掉進白矮星。 拱星盤的不穩定性或白矮星因物質累積而觸發短暫且劇烈的核融合，讓它的亮度急遽變亮。觀測顯示，蛇夫座RS星現在已快速變暗。 這幅望遠鏡影像是在2月16日清晨拍攝的，地點是美國新墨西哥州的RAS天文台。 [/color]
[size=2]資料來源: Scientific American
Department of Physics, NCKU[/size][color=white][size=1]
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