Explanation:
Also known by the popular name the "Little Dumbbell Nebula",
M76 is
one of the fainter objects listed in Charles Messier's 18th century
Catalog of
Nebulae and Star Clusters.
Like its better-known namesake M27
(the Dumbbell Nebula), M76 is recognized
as a planetary
nebula - a gaseous shroud cast off by a
dying sunlike star.
The nebula itself is thought to be shaped more like a donut, its
central box-like appearance
due to our nearly edge-on view.
Gas expanding more rapidly away from the donut hole produces the
more extensive, far flung material in
this remarkable image
that uses narrow-band
filters to highlight the
emission from hydrogen (in red) and
oxygen atoms (in greenish blue).
In particular, complex oxygen emission features are seen
above and below the main nebula to a degree not detected
in most images of M76.
Distance estimates place M76 about 3 to 5 thousand light-years away
toward the heroic constellation
Perseus,
making the nebula over a
light-year in diameter.
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