Open Cluster Messier 37
M 37 (NGC 2099) is the most beautiful of the three bright Messier star clusters in the constellation Auriga (Fuhrmann). The other two are M 36 and M 38. It was first found in 1654 by Giovanni Hodierna and then rediscovered on September 2, 1764 by Charles Messier. Messier wrote: «Cluster of small stars, not far from the previous one, on the parallel of χ Aurigae; the stars are smaller, closer together, and contain nebulae; It is difficult to see the stars with an ordinary 3.5-foot telescope: this cluster is inscribed on the map of the second comet from 1771, Mem. Akad. 1777.» 
The star cluster contains about 150 stars up to 12.5 magnitudes. In total, it should have more than 500 stars. The stellar population differs from that of M 36 and is believed to be older. The age is estimated to be just over 200 million years. The youngest stars are of type B9V and most of the other bright stars are main sequence A stars. The cluster also contains at least a dozen red giants. The brightest of these is 9.5 mag bright and stands out near the center like a red ruby in a field of diamonds. The distance of the star cluster is at 1383 pc to 1400 pc, slightly more than M 36. [4, 145, 196]
The open star cluster is located east of the pentagon in the constellation Auriga (Charioteer) and is visible to the naked eye on a dark night. The best observation time is September to April.