猎户(Orion)座中的星云状物质。图中下方是M78小星云，上方是猎户座大星云。猎户座大星云直径约16光年，距离1500光年，质量为太阳质量的300倍左右。
The Horsehead Nebula :
The Horsehead Nebula, B33, is the dark nebula in front of the bright red emission nebula IC 434. Dark Nebulae are clouds of dust in space that obscure the stars behind them. Emission nebulae are clouds of glowing ionized gas. Reflection nebulae do not shine by their own light, but are visible because they reflect the light of nearby stars. Along with the Orion Nebula, M42, it is part of a very large complex that is a stellar nursery where stars are forming out of the dust and gas. Located about 1,500 light years away, this complex is the closest star forming region to our own solar system.
猎户座(Orion)中的马头(Horsehead)星云B33，它是个暗星云。
http://www.astron.sh.cn/picbase/star/xy.html
