Astronomy Picture of the Day

Explanation: In silhouette against a crowded star field toward the constellation Scorpius, this dusty cosmic cloud evokes for some the image of an ominous dark tower. In fact, clumps of dust and molecular gas collapsing to form stars may well lurk within the dark nebula, a structure that spans almost 40 light-years across the gorgeous telescopic view. Known as a cometary globule, the swept-back cloud, extending from the lower left to the head (top of the tower) right and above center, is shaped by intense ultraviolet radiation from the OB association of very hot stars in NGC 6231, off the left edge of the scene. That energetic ultraviolet light also powers the globule's bordering reddish glow of hydrogen gas. Hot stars embedded in the dust can be seen as bluish reflection nebulae. This dark tower, NGC 6231, and associated nebulae are about 5,000 light-years away.

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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Publications with keywords: Scorpius - dark nebula - cometary globule
Publications with words: Scorpius - dark nebula - cometary globule
See also:

• Dark Clouds in Aquila
• In Wolf s Cave
• The Dark Tower in Scorpius
• Sisters of the Dusty Sky
• Dark River Wide Field
• Dim World, Dark Nebula
• Stardust in Perseus

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