M37 (NGC 2099) is one of three bright open clusters in the southern part of the constellation Auriga, along with M36 and M38. All three were first recorded by Giovanni Hodierna before 1654. All three lie at similar distances of about 4,000 light-years. M37 is the richest and brightest of the trio. It contains approximately 150 stars brighter than magnitude 12.5 and perhaps 500 stars in total. The fact that it contains a dozen or so red giants and that its hottest main sequence star is of type B7V suggests an age for the cluster of about 300 million years.