Explanation:
"Nebula at the right foot
of
Andromeda ... " begins the description
for the 76th object in Charles Messier's 18th century Catalog
of
Nebulae and Star Clusters.
In fact, M76 is
one of the fainter objects on the Messier list and
is also known by the popular name of the "Little Dumbbell Nebula".
Like its brighter 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, while the
box-like appearance of its brighter central
region is due to our nearly edge-on view.
Gas expanding more rapidly away from the donut hole produces the
fainter loops of far flung material.
The fainter material is emphasized in this composite image, highlighted
by showing emission from hydrogen atoms in orange and oxygen atoms
in complementary blue hues.
The nebula's dying star can be picked out in
the
sharp false-color image as the blue-tinted star near the
center of the box-like shape.
Distance estimates place M76 about 3 to 5 thousand light-years away,
making the nebula over a
light-year in diameter.
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