Open star cluster M-37 was discovered by Hodierna before 1654 as 'a nebulous patch' and re-discovered by Le Gentil in 1749. Other nearby star clusters in Auriga include M-36 and M-38, both also first observed by Hodierna and Le Gentil.
Charles Messier (Sept. 2nd, 1764):
'A cluster of small stars a little removed from the preceding(M 36), the stars are smaller, more close together and enclosing some of the nebulosity. With an ordinary telescope of 3.5 feet, it is difficult to see the stars. Reported on chart of comet of 1771. Diam. 9 arc minutes.'
'A magnificent object; the whole field being strewn, as it were, with sparkling gold dust and the group is resolvable into about 500 stars from 10-14 mag. Besides outliers.'
'Even in small instruments, extremely beautiful; one of the finest of its class. Gaze at it well and long!'
Quote from Dreyer's New General Catalog(NGC) for NGC 2099:
Cluster, rich in stars, westward compressed middle, stars large & small; = M37.
Quote from Burnham's Celestial Handbook:
A superb galactic star cluster for telescopes of all sizes, usually considered the finest of the three Messier open clusters in Auriga........ It will probably look like a nebula in instruments smaller than 12-inch aperture, but in anything larger than a 2-inch, some of the individual stars will be seen easily. "A diamond sunburst", as C.E. Barns described it, this striking cluster is a virtual cloud of glittering stars. ...... The Earl of Rosse commented on the "wonderful loops and curved lines of stars", which seem also to be a feature of some other galactic clusters, as M-35 in Gemini, for example. M37 contains about 150 stars down to magnitude 12.1; the total population may be in excess of 500 stars. The stellar population of this cluster is significantly different from that of M-36, and suggests an older and more evolved group of stars. An age of somewhat over 200 million years is indicated by current knowledge of stellar evolution. The earliest type star in the cluster is of spectral class B9 V, and the majority of the other bright members are main sequence A stars with absolute magnitudes of about -1. But the cluster also contains at least a dozen red giants. The brightest of these has a visual magnitude of about 9.2 and stands out near the cluster center "like a ruby on a field of diamonds".
The best distance and diameter estimates are: distance = 4,600 light years, diameter = 25 light years. Hopefully the recent data from the Hipparcos satellite will provide accurate figures.
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George Normandin, KAS
January 31st, 2000