M 38
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M 38

February 18, 2005
Open Cluster M38 (NGC 1912), type 'e', in Auriga

Right Ascension: 05 : 28.4 (h:m)
Declination: +35 : 50 (deg:m)
Distance: 4.2 (kly)
Visual Brightness: 7.4 (mag)
Apparent Dimension: 21.0 (arc min)

Discovered by Giovanni Batista Hodierna before 1654.

Lying only 2.5 degree northwest (preceding) of M36, this cluster was silently discovered by Hodierna before 1654, and independently found by Le Gentil in 1749. Charles Messier included it in his catalog on September 25, 1764.

Its brightest stars form a pattern resembling the Greek letter Pi, or (according to Webb) an "oblique cross". At its distance of 4,200 light years, its angular diameter of about 20' corresponds to about 25 light years, similar to that of its more distant neighbor M37. It is of intermediate age (about 220 million years according to the Sky Catalog 2000) and contains a yellow giant of mag 7.9 and spectral type G0 as its brightest member - this corresponds to an absolute magnitude of -1.5, or a luminosity of 900 suns. For comparison, the Sun would appear as faint as only mag 15.3 from the distance of M38 !

Kenneth Glyn Jones has a significantly smaller distance of only 2,750 light years. The Trumpler class of M38 is given as II,2,r by all sources.

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