Messier Index/M37

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Messier 37
M37a.jpg
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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