Messier 34

Open Cluster M34 (NGC 1039), type 'd', in Perseus

Discovered by Giovanni Batista Hodierna before 1654.

Open star cluster Messier 34 (M34, NGC 1039) is an intermediate aged open cluster of about 100 stars (according to H.S. Hogg), and lies about 1,400 light years and is scattered over 35 arc minutes, more than the diameter of the full Moon. This angular diameter corresponds to a linear 14 light years; Wallenquist has estimated a little more (42' corresponding to 18.5 light years).

This cluster was classified as of Trumpler type I,3,m (Sky Catalog 2000) or II,3,r (Götz). It appearance is influenced by a nearby non-member of mag 7.3, while the brightest member star is of magnitude 7.9.

The age of M34 was estimated at 110 million years by Van Hoerner in 1957, while the Sky Catalog 2000 gives a more modern value of 190 million years. This value has recently been updated to 180 million years, according to the new calculations of G. Meynet's Geneva Team.

Considering the spatial motion of M34 and other clusters, O.J. Eggen (1983) found it co-inciding with that of several others, including the Pleiades (M45), NGC 2516, IC 2602, the Alpha Persei Cluster (Melotte 20) and the Delta Lyrae Cluster (Stephenson 1). He called this group of clusters the "Local Association."

M34 was probably first found by Giovanni Batista Hodierna before 1654, and independently rediscovered by Charles Messier in on August 25, 1764.

Open cluster M34 can quite easily be found (even with the naked eye under good conditions as a faint nebulous patch) as it lies just north of the line from Algol (Beta Persei) to Gamma Andromedae. It is resolved into stars even in 10x50 binoculars, and best at low magnifications in telescopes. Mallas describes the form displayed by the brightest stars as a distorted "X", while Kenneth Glyn Jones finds them to form three distinctly curved arms, radiating out from the center. About 20 brighter stars, filling a 10' area, are surrounded by a larger number of fainter outlying members, larger amateur instruments showing a total of about 80 stars. Many stars are arranged in pairs, notably the optical double h 1123 (cataloged by John Herschel) near the cluster's center (two stars of mag 8.0 to 8.5 of spectral type A0, separated 20" in position angle 248 deg), and Otto Struve 44 near the SE edge (A: 8.4, B: 9.1, separated 1.4" in PA 55 deg) - this double was discovered by Otto Struve in 1840 with a 15-inch refractor.

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