Explanation:
In visible
light images, over a thousand galaxies are seen to
lie within a volume about 20 million light-years across in
the rich Coma Galaxy Cluster.
But infrared images of the Coma Cluster have now been used
to add thousands more to the Coma's galaxy count in the form
of previously
undiscovered dwarf galaxies.
This composite combines infrared
Spitzer Space Telescope image data
(red and green) with visible light Sloan Sky Survey data (blue)
for the central part of the cluster.
Over 1 degree wide, the field is
dominated by two giant
elliptical galaxies in blue.
Still, many of the small green smudges (see magnified inset)
are identified as dwarf galaxies,
roughly comparable to the
Small Magellanic Cloud.
Dwarf galaxies are thought to form
first, providing building blocks for larger galaxies.
The well-studied,
friendly,
Coma Cluster
is 320 million light-years away.
