Messier 34

Lore & Background

Messier 34 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 γ (Andromedae). In an ordinary telescope of 3 feet one can distinguish the stars.' Based on the distance modulus of 8.38, it is about 470 parsecs (1,500 ly) away. The cluster spans about 35′ on the sky, which translates to a true radius of 7.5 light years at such distance. The cluster is just visible to the naked eye in very dark conditions, well away from city lights, and can be seen in binoculars when light pollution is low.

The age of this cluster lies between the ages of the Pleiades open cluster at 100 million years and the Hyades open cluster at 800 million years. Specifically, comparison between noted stellar spectra and the values predicted by stellar evolutionary models suggest 200–250 million years. This is roughly the age at which stars with half a solar mass enter the main sequence. The average proportion of elements with higher atomic numbers than helium, termed metallicity, has a value of [Fe/H] = +0.07 ± 0.04, equivalent to a 17% higher proportion of iron compared to the Sun. Other elements show a similar abundance, save for nickel which is underabundant.

At least 19 members are white dwarfs, stellar remnants of progenitor stars of up to eight solar masses that have evolved through the main sequence and no longer have thermonuclear fusion to generate energy. Seventeen of these are of spectral type DA or DAZ, while one is a type DB and the last is a type DC.

Reader's Guide

Messier 34 is significant as a relatively near open cluster that provides a useful benchmark for stellar evolution studies. Its age of 200–250 million years places it between the well-known Pleiades and Hyades clusters, allowing astronomers to compare stellar development at an intermediate stage. The cluster contains about 400 stars ranging from 0.12 to 1 solar mass, and its metallicity is slightly higher than the Sun's, with a 17% greater iron abundance. The presence of at least 19 white dwarfs, including various spectral types (DA, DAZ, DB, DC), offers insight into the end stages of stars up to eight solar masses. Discovered before 1654 by Hodierna and cataloged by Messier in 1764, it has been observed and described historically. Its visibility under dark skies—naked eye in very dark conditions and through binoculars with low light pollution—makes it accessible to amateur astronomers. The cluster's distance of about 1,500 light years and true radius of 7.5 light years are well established through its distance modulus and angular size.

Did You Know?

• The cluster has a metallicity 17% higher in iron than the Sun.
• At least 19 members are white dwarfs, including types DA, DAZ, DB, and DC.
• Its age of 200–250 million years falls between the Pleiades (100 million years) and Hyades (800 million years).