Astronomy Picture of the Day
探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。
2006年04月17日（农历二〇〇六年三月二十）
http://www.bjp.org.cn/files/2006 ... loop_erdman_big.jpg
在马头星云周围的巴纳德环
版权及影像提供：Peter Erdman (Embry-Riddle U.)
Explanation: Why is the Horsehead Nebula surrounded by a bubble? Although glowing like an emission nebula, the origin of the bubble, known as Barnard's Loop, is currently unknown. Progenitor hypotheses include the winds from bright Orion stars and the supernovas of stars long gone. Barnard's Loop is too faint to be identified with the unaided eye. The nebula was discovered only in 1895 by E. E. Barnard on long duration film exposures. The above image was taken in a single specific color emitted by hydrogen to bring out detail. To the left of the Horsehead Nebula, visible as the small dark indentation near the image top, is the photogenic Flame Nebula.
解释：为什么马头星云周围环绕着泡泡？尽管像发射星云，猎户座的泡泡，为人所熟知的巴纳德环，到现在还有很多未知之处。起源假说中包括猎户座中明亮的恒星吹出的风，以及早期超新星爆炸留下的物质。巴纳德环太昏暗以致肉眼无法辨认。仅在1895年巴纳德环才在长时间曝光的星云照片上被发现。上面图像是在氢元素放射出单一特殊颜色下拍摄的，以便突出巴纳德环的细节。在左侧的马头星云，靠近图像的顶部，可见小而黑暗的锯齿状物，那便是上镜的火焰星云。
Tomorrow's picture: open space