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2005 年 12 月 23 日
http://www.bjp.org.cn/apod/2005-12/23/content_5764.htm
玫瑰星云里的氢气和尘埃
版权：Nick Wright (University College London), IPHAS Collaboration
说明：在麒麟座有一块巨大的分子云，离我们约3,000xx光年，在它的边缘处，黑暗的尘埃纤维遮住发光的氢气发出的光，形成黑色的剪影。玫瑰星云的特写镜头生动地显示了，这个区域正在进行恒星形成，并且黑暗的纤维结构被来自年轻热星的星风和辐射塑造成型。年轻星发出的紫外辐射也把围绕氢原子的电子电离。当电子和原子再次结合时，他们就会发出波长更长、能量更低的光，即著名的明亮的特征谱线。在可见光波段，特征谱线中最强的发射线是光谱中红端的部分，就是人们熟知的“氢—α”或“H—α”。对我们银河系H—α的发射进行巡天是ＩＰＨＡＳ的一部分，而这张图就是一次巡天的结果，它横跨约xxx (30 x 20 arcmin)光年。（翻译：刘媛媛）
明日图片：Earthrise
Hydrogen and Dust in the Rosette Nebula
Credit: Nick Wright (University College London), IPHAS Collaboration
Explanation: At the edge of a large molecular cloud in Monoceros, some 3,000 light years away, dark filaments of dust are silhouetted by luminous hydrogen gas. The close up view of the Rosette Nebula dramatically suggests that star formation is an on going process in the region, with dark filaments sculpted by winds and radiation from hot, young stars. Ultraviolet radiation from the young stars also strips electrons from the surrounding hydrogen atoms. As electrons and atoms recombine they emit longer wavelength, lower energy light in a well known characteristic pattern of bright spectral lines. At visible wavelengths, the strongest emission line in this pattern is in the red part of the spectrum and is known as "Hydrogen-alpha" or just H-alpha. Part of IPHAS, a survey of H-alpha emission in our Milky Way Galaxy, this image spans about 25 light-years. [/center]
[ Last edited by Edelweiss on 2005-12-23 at 08:17 PM ]