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 upper right to the head (top of the tower) left and
below 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 small bluish
reflection nebulae.
This dark tower,
NGC 6231, and
associated nebulae are about 5,000 light-years away.
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