Messier 38 orM38, also known asNGC 1912 orStarfish Cluster,[4] is anopen cluster ofstars in theconstellation ofAuriga. It was discovered byGiovanni Batista Hodierna before 1654 and independently found byGuillaume Le Gentil in 1749. The open clustersM36 andM37, also discovered by Hodierna, are often grouped together with M38.[5] Distance is about 1.066 kpc (3,480 ly) away fromEarth.[2] The open cluster NGC 1907 lies nearby on the sky, but the two are most likely just experiencing a fly-by, having originated in different parts of the galaxy.[1]
The cluster's brighteststars form a pattern resembling the Greek letterPi or, according to Webb, an "oblique cross".Walter Scott Houston described its appearance as follows:[6]
Photographs usually show a departure from circularity, a feature quite evident to visual observers. Older reports almost always mention a cross shape, which seems more pronounced with small instruments. A view with a 24-inch reflector on a fine Arizona night showed the cluster as irregular, and the host of stars made fruitless any effort to find a geometrical figure.
At its distance of 1066 pc., its angular diameter of about 20 arc minutes corresponds to about 4.0 parsecs (13 light years), similar to that of its more distant neighbor M37. It is of intermediate age at about 290 million years.[2] From the population of about 100 stars,[7] this open cluster features a prominent yellow giant with theapparent magnitude +7.9 andspectral type G0 as its brightest member. This corresponds to anabsolute magnitude of -1.5, or a luminosity of 900 Suns. For comparison, theSun would appear as a faint magnitude +15.3 star from the distance of M38.
