M 45, better known as the Pleiades, is an open cluster which is easily visible
with the unaided eye. It is sometimes called "The Seven Sisters," and with a
dark sky and good eyesight you can probably see 6 or 7 of the brightest stars
in the cluster (actually, there are reports from centuries past of particularly
well-sighted observers seeing up to 14 members of the cluster without a telescope).
The blue reflection nebula throughout the cluster is caused by the light from
these bright stars reflecing off a cloud of gas and dust which the cluster happens
to be passing through at this time -- it is not the leftovers of the cloud out of
which this cluster formed. M 45 is 380 light years from the earth.

See also a more "close-up" image of this object near the bottom of the DSLR page.

Image data:
Camera: Canon 350 XT (modified)
Telescope: William Optics 66mm + 0.8x reducer / field flattener
Exposure: ISO 800, 5 minutes x 12