Messier 37 — Open Cluster in Auriga

M37 is the brightest and richest of the three Messier open clusters in Auriga, located about 4,500 light-years from Earth. It contains approximately 500 stars and spans about 24 light-years in diameter, with an apparent size of roughly 24 arcminutes. The cluster is estimated to be about 350-550 million years old — old enough that many of its more massive stars have evolved off the main sequence. M37 contains at least a dozen red giant stars, giving it a distinctive appearance with orange-hued stars scattered among its blue-white members. It is one of the finest open clusters in the northern sky.

Located about 3.5 degrees southeast of M36 in Auriga. Of the three Auriga Messier clusters, M37 is the richest and most rewarding to observe. In binoculars, it appears as a bright, granular haze. A 4-inch telescope at 80-100x resolves dozens of stars packed into a rich, glittering field — the view is often compared to sugar sprinkled on black velvet. Look for the noticeably orange-red star near the cluster center, which contrasts beautifully with the surrounding blue-white members. An 8-inch telescope at 100-150x reveals over 100 stars in a stunning display. Best observed from November through March.

Discovered by Giovanni Battista Hodierna before 1654. Independently rediscovered by Charles Messier on September 2, 1764. Messier described it as a cluster of small stars with no nebulosity. M37 has been extensively studied for stellar evolution because its intermediate age places many of its stars at interesting evolutionary stages — particularly the transition to the red giant branch. Over 20 white dwarfs have been identified in the cluster.