The Great Spiral Galaxy
in Andromeda (aka M31), a mere 2.5 million
is the closest
large spiral to our own Milky Way.
Andromeda is visible to the unaided eye as a small, faint, fuzzy patch,
but because its surface brightness is so low, casual
can't appreciate the galaxy's impressive extent in
planet Earth's sky.
This entertaining composite image compares the
of the nearby galaxy
to a brighter, more familiar celestial sight.
In it, a
exposure of Andromeda, tracing beautiful blue star
clusters in spiral arms far beyond the bright yellow core,
is combined with a typical view of a nearly full Moon.
Shown at the same
angular scale, the Moon covers
about 1/2 degree on the
sky, while the galaxy is clearly several times that size.
The deep Andromeda exposure also includes two bright satellite
galaxies, M32 and
Adam Block and