Open Cluster M34 in Perseus

Messier 34 (also known as M 34 or NGC 1039) is an open cluster in the constellation Perseus. It was probably discovered by Giovanni Batista Hodierna before 1654 and included by Charles Messier in his catalog of comet-like objects in 1764. Messier described it as, "A cluster of small stars a little below the parallel of ? (Andromedae). In an ordinary telescope of 3 feet one can distinguish the stars." Based on the distance modulus of 8.38, this cluster is located at a distance of about 470 parsecs, or 1,500 light years.[3] For stars in the range from 0.12 to 1.0 solar masses, M34 contains an estimated 400 members.[5] It spans about 35' on the sky which translates to a true radius of 7 light years.[citation needed] The cluster is just visible to the naked eye in very dark conditions, well away from city lights. It is well seen in binoculars. The age of this cluster lies between the respective ages of the Pleiades open cluster at 100 million years and the Hyades open cluster at 800 million years. Comparisons between the observed stellar spectra and the values predicted by stellar evolutionary models gives an age estimate of 200 to 250 million years for M34. This is roughly the age at which stars with 0.5 solar masses enter the main sequence. By comparison, stars like the Sun enter the main sequence after 30 million years.