Messier 38, NGC 1912 - Starfish Cluster

Messier 38 (NGC 1912) is one of the three Messier open clusters in the southern part of Auriga. It has been nicknamed the "Starfish" cluster, though the origin of this moniker is uncertain.

M 38 cluster was discovered by Giovanni Batista Hodierna before 1654, and independently found by Le Gentil in 1749. Charles Messier included it in his catalog in 1764.

Lying only 2.5° northwest of M 36, M 38 is about the same size as M 37, but it is somewhat fainter at magnitude 7.4. Messier 38 is a rich, irregularly round group, 20' in diameter, containing over a hundred stars, many of 9th magnitude or brighter. The cluster's brightest stars form an asterism shaped like the Greek letter π. M 38 stands out well from the evenly-distributed background star field. Visually it is the second most impressive of Auriga's "big three" Messier open clusters (M 37, M 38, and M 39).

M 38 lies at a distance of 4200 light-years, and has a diameter of 25 light years, about the same as M 37. It is is of intermediate age, about 220 million years old; its hottest member a class B5 star having an absolute magnitude of about -1.5. The cluster also contains a number of A-type main sequence stars, and several G-type giants. The brightest cluster member is a yellow GO giant with a visual magnitude of 7.9 and an actual luminosity of about 900 suns. By comparison, if we could view our Sun from the distance of M 38, it would appear as a 15th magnitude object!