Object Analysis

Messier 103 (M103) is an open cluster in the constellation Cassiopeia. It was discovered by Pierre Méchain in 1781 and was the last object Messier personally added to his catalog. It is one of the most distant open clusters in the Messier catalog, located about 10,000 light-years from Earth.

M103 is a relatively small cluster, containing about 40 confirmed members. The stars are arranged in a distinct fan or Christmas tree shape. The cluster is dominated by a bright 7th-magnitude star, though this star is actually a foreground object that is not a true member of the cluster. The true members are mostly hot, blue-white stars.

It is a young cluster, estimated to be about 25 million years old. Because it is so far away, it appears small and compact in binoculars, looking like a hazy "knot" of light. In a telescope, it resolves into a striking, colorful group, with a prominent red giant star near its center providing a beautiful contrast to the blue-white majority.