| Messier 37 | |
|---|---|
 M37 open cluster, source: NOAO | |
| Observation data (J2000.0 epoch) | |
| Constellation | Auriga |
| Right ascension | 5h 52m 19s |
| Declination | +32° 33′ 2″ |
| Distance | 4.4 kly (1.3 kpc) |
| Apparent magnitude (V) | 6.2 |
| Apparent dimensions (V) | 24′ |
| Other designations | w:NGC 2099 |
Messier 37 (also known as M37 or NGC 2099) is the richest w:open cluster in the w:constellation Auriga. It was discovered by w:Giovanni Batista Hodierna before w:1654.
Messier 37 is the brightest of the three open clusters in Auriga. M37 was missed by w:Le Gentil when he rediscovered M36 and M38 in 1749. w:Charles Messier independently rediscovered M37 in September of w:1764 but all three clusters were recorded by Hodierna before 1654. All three clusters were generally unknown until w:1984.
M37 is roughly 300 million years old and contains over 500 stars with roughly 150 stars brighter than magnitude 12.5. M37 also contains at least a dozen w:red giants with the hottest w:main sequence star of w:spectral type B9V. Its distance is between 3,600 to 4,700 w:light years and the apparent diameter of 24' corresponds to a w:linear extension of about 20 to 25 light years. It is classified as Trumpler type I,1,r or I,2,r.
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