M37 - NGC 2099

Messier 37 (NGC 2099) is the brightest and richest of the three prominent Messier open clusters in the constellation Auriga, located approximately 4,500 light-years from Earth. It contains roughly 500 stars within a diameter of about 24 light-years and shines at a combined apparent magnitude of about 6.2. M37 is estimated to be around 300 to 500 million years old, making it the oldest of the three Auriga clusters, and old enough for a significant number of its more massive stars to have evolved into red giants. The cluster contains at least a dozen red giants, whose warm orange colors scattered among the predominantly blue-white main-sequence stars create the beautiful "salt and pepper" effect that gives the cluster one of its nicknames. This color contrast is one of the cluster's most appealing visual characteristics. M37 was first recorded by Giovanni Battista Hodierna before 1654 and independently discovered by Messier in 1764. The cluster spans about 24 arcminutes in apparent diameter and is best viewed at moderate magnification, which reveals a dense, rich field of stars that fills the eyepiece with a shimmering carpet of light. A star of roughly 9th magnitude sits near the center of the cluster and serves as a useful reference point. M37 is widely regarded as one of the finest open clusters in the entire sky and is a highlight of winter observing for Northern Hemisphere astronomers. Through binoculars it appears as a bright, grainy haze, while a telescope of any size reveals individual stars. The full beauty of the cluster emerges in instruments of 4 inches or more, where the interplay of red and blue stars becomes apparent.

Contains approximately 500 stars spanning 24 light-years at a distance of 4,500 light-years, with an age of 300 to 500 million years.