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 this
gorgeous telescopic portrait.
Known as a
cometary globule, the swept-back cloud,
extending from the lower right to the head (top of the tower) left and
above center, is shaped by intense ultraviolet radiation from
the OB association of very hot
stars
in NGC
6231, off the upper 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.
