M37 is a type of star cluster known as an open cluster. Open clusters can contain between a dozen to a few hundred stars. Some of the stars within the cluster are more visible while others are less obvious. In comparison to globular clusters, which tend to be symetrical in shape, open clusters tend to take on the shape of their nebula. The stars in open clusters are relativey new (young to middle age) and the groups are amoung the youngest of any stars in the sky. Typically the stars are vastly spread out in the sky at anywhere from 30-90 light years across.

M37 is the brightest of the three open clusters in the Auriga constellation (below, south middle). It was first identified in 1764,

by Charles Messier. It contains approximately 500 stars. As open clusters go M37 is relatively small at a linear extension of 20-25 light. The age of the cluster is estimated to be around 300,000,000 years.

The photo at the top of the page was taken using a 16" Cassegrain telescope at the Sherman W. Schultz Observatory of Macalester College in St. Paul, MN on November 24, 1999. Conditions on that night the image was taken were good. RGB filters were used to collect the image, with a four second exposure time for the red filter a six second exposure time for the green filter and a 12 second exposure time for the blue filter. To minimize the excessive amount of blue the colors were altered towards the red. The signal-to-noise ratio (30) could definitely be improved upon, as a ratio of one hundred is preferred. This could be done by increasing the exposure time or taking images under better sky conditions.