IC 2118: The Witch Head Nebula（IC2118：女巫头星云）

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[center]Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2005 December 27

http://antwrp.gsfc.nasa.gov/apod ... /witch_hubl_big.jpg
IC 2118: The Witch Head Nebula
Credit & Copyright: Bernhard Hubl
Explanation: Double, double toil and trouble; Fire burn, and cauldron bubble -- maybe Macbeth should have consulted the Witch Head Nebula. This suggestively shaped reflection nebula is associated with the bright star Rigel in the constellation Orion. More formally known as IC 2118, the Witch Head Nebula glows primarily by light reflected from Rigel, located just outside the top right corner of the above image. Fine dust in the nebula reflects the light. The blue color is caused not only by Rigel's blue color but because the dust grains reflect blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers in Earth's atmosphere are molecules of nitrogen and oxygen. The nebula lies about 1000 light-years away.
IC2118：女巫头星云

影像提供：Bernhard Hubl

说明：努力吧！忙碌吧！猛烈的柴火烧煮着沸腾的大锅 (莎翁名剧－麦克白)。也许，麦克白 (Macbeth)该去祈求女巫头星云呢。女巫头星云，是一个依照它的形状而命名的反射星云，它位在猎户座内，而且受到亮星参宿七 (Rigel)的影响。女巫头星云的正式的名称为IC 2118，在上面这张图片中，参宿七并不在里头，而是位于照片右上侧的外面，星云会发光，是因为星云内微细的尘埃，反射参宿七的星光所形成的。星云中清晰的尘埃反射光线。女巫头星云的颜色是蓝色的，这不只是因为参宿七是蓝色的，而且也是因为星际尘埃的颗粒，对蓝光的散射效率比红光要好。所以，这与地球白天的天空是蓝色的道理是一样的，只是散射源不同而已；地球的大气是由阳光经由空气中的氮分子与氧分子散射所造成的。这个星云与地球相距约1000光年。

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[ Last edited by 夜猫子 on 2005-12-27 at 05:42 PM ]

夜猫子

象一团轻烟！

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美妙星空！