Messier 38 or M38, also known as NGC 1912 or Starfish Cluster,[4] is an
open cluster of
stars in the
constellation of
Auriga. It was discovered by
Giovanni Batista Hodierna before 1654 and independently found by
Le Gentil in 1749. The open clusters
M36 and
M37, also discovered by Hodierna, are often grouped together with M38.[5] Distance is about 1.066
kpc (3,480
ly) away from
Earth.[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 brightest
stars form a pattern resembling the Greek letter
Pi 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 the
apparent magnitude +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 a faint magnitude +15.3 star from the distance of M38.
