The Horsehead and Flame Nebulas
Image Credit & Copyright: Wissam Ayoub
Explanation: The Horsehead Nebula is one of the most famous nebulae on the sky. It is visible as the dark indentation to the orange emission nebula at the far right of the featured picture. The horse-head feature is dark because it is really an opaque dust cloud that lies in front of the bright emission nebula. Like clouds in Earth’s atmosphere, this cosmic cloud has assumed a recognizable shape by chance. After many thousands of years, the internal motions of the cloud will surely alter its appearance. The emission nebula’s orange color is caused by electrons recombining with protons to form hydrogen atoms. Toward the lower left of the image is the Flame Nebula, an orange-tinged nebula that also contains intricate filaments of dark dust. Two prominent reflection nebulas are visible: round IC 432 on the far left, and blue NGC 2023 just to the lower left of the Horsehead nebula. Each glows primarily by reflecting the light of their central star.
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马头星云与火焰星云
影像版权与提供: Wissam Ayoub
说明: 马头星云是地球天空中最著名的星云之一。在这张影像右缘的红色发射星云上，那片黝黑斑块就是马头星云。而“马头”会如此黝黑，因它是这片明亮发射星云前方的不透光尘埃云。类似地球大气中的云朵，这团宇宙云只是恰巧有个我们很熟悉的形状。再经过数千年，星云内部的运动将改变它的外观。发射星云橙红的色泽，是来自电子和质子复合组成氢原子时所放出的光。而影像左下方的天体，则是橙色的火焰星云，其内有形状繁复的丝状黝黑尘埃。这幅影像更记录了2个鲜明的反射星云，它们分别是左缘形状浑圆的IC 432和马头星云左下方泛蓝的NGC 2023，它们的色泽来自尘埃反射中心星的星光。
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