Explanation:
Near picture center, the helmet-shaped structure with
wing-like appendages is popularly called
Thor's Helmet.
Cataloged as NGC 2359, the striking nebula is located about
15,000 light-years away in the constellation
Canis
Major.
The helmet is actually more like
a
cosmic bubble, blown as the
wind from the bright, massive star near the bubble's center sweeps
through the surrounding molecular cloud.
Known as a
Wolf-Rayet star, the energetic star is a blue giant
thought to be in a brief,
pre-supernova stage of evolution.
The remarkable color composite
combines broad and narrow band images -
including a deep exposure recorded with an
H-alpha filter.
The H-alpha image traces the light from
the region's glowing atomic hydrogen gas.
Heroically sized even for a
Norse god,
this Thor's Helmet is about 30 light-years across.
