M18 is a small open cluster of about 20 stars
located in the constellation Sagittarius. It lies about 5,000
light-years away with a diameter of about 17 light-years. The
cluster contains only 12 fairly bright stars, and the cluster is
rather loose in appearance. It is not one of the best examples
of a galactic cluster, but it is a pretty sight in a small
telescope. This a fairly young cluster, containing bright blue
as well as yellow and orange stars.