M 31, the "Andromeda Galaxy", is the large galaxy nearest to
our own (estimates range from 2.4-2.9 million light years away).
M 31 is, like our Milky Way, a spiral galaxy, though at more than
200,000 light year across it is more than twice as large as the
Milky Way. It is easily visible to the naked eye, appearing as a
fuzzy smudge of light. The eye can see only the bright central
region, but the full width of the galaxy is as long as 6 full
moons in the sky (this image does not show the full extent of M 31).
M 31, unlike most galaxies, is approaching the Milky Way (at 100
kilometers / second). Our galaxy and M 31 will meet someday, and
after a very long dance will merge into one huge galaxy.
But that day is billions of years away. Above M 31 you can see one of
its small companion galaxies, M 32 above.

Image data:
Camera: Canon 350XT
Exposure: ISO 800, 30 seconds x 60
Telescope: 10" Schmidt-Newtonian