NASA 美国宇航局的每日一图 3月份
发布: 2009-1-14 17:53 | 作者: webmaster | 来源: 本站原创 | 查看: 179次
2008 March 23 
影像提供: FORS Team, 8.2-meter VLT Antu, ESO 说明: 恒星都跑到那儿去了？以前我们认为它是天空中的一个洞，现在则知道它是个暗分子云。 在这个分子云中，高密度的尘埃和分子云气几乎完全挡住了背景恒星所发出的可见光。 这个诡异暗分子云的内部，可能是宇宙中最阴冷且最孤独的地方之一。 上面这张照片里的星云是位于蛇夫座的巴纳德68，它是最著名的暗星云之一。 在星云的中心附近完全看不到任何的恒星，显示巴纳德68离我们不远，量测结果认为它离我们约有五百光年远，大小约有半光年。 我们现在还不是很清楚像巴纳德68这种分子云是如何形成的，但我们知道它们很可能是新恒星将形成的地方。我们可以用红外光透视这类云气，一窥星云内部的状态。
Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. It is possible to look right through the cloud in infrared light.
Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. It is possible to look right through the cloud in infrared light.
