Explanation:
This helmet-shaped cosmic cloud with
wing-like appendages is popularly called
Thor's
Helmet.
Heroically sized even for a
Norse god,
Thor's Helmet is about 30 light-years across.
In fact, the helmet is actually more like
an interstellar bubble, blown as a fast
wind from the bright, massive star near the bubble's center sweeps
through a surrounding molecular cloud.
Known as a
Wolf-Rayet star, the central star is an
extremely hot giant thought to be in a brief,
pre-supernova stage of evolution.
Cataloged as NGC 2359, the nebula is located about
15,000 light-years away in the constellation
Canis
Major.
The sharp
image captures striking details of the
nebula's filamentary structures and also
records an almost emerald color from strong emission
due to oxygen atoms in the glowing gas.
