Call on the Coma Star Cluster

The Coma Star Cluster (Melotte III). Image: Graham Wilcock.

Melotte III is a sprawling open cluster that can be spotted with the naked eye tucked away in far north-west of Coma Berenices. It’s popularly named the Coma Star Cluster and provides a pleasant alternative at the peak of galaxy observing season. Melotte 111 is named for the English astronomer Philibert Jacques Melotte (1880–1961), who included it in his catalogue of star clusters in 1915..

The Coma Star Cluster is large and loose, covering a four to five degrees of sky. It is a challenge to pick out in a moderately light-polluted sky, taking on a fuzzy appearance. Magnitude +4.4 gamma (γ) Comae Berenices [Com]) is its brightest member and marks its northern extremity. Five of its fifth-magnitude stars, Flamsteed designated 12, 13, 14, 16 and 17 Com, form a triangular pattern that’s well seen through 10 x 50 binoculars, probably the best instrument through which to observe Melotte III, as a small telescope won’t show the cluster to similar advantage owing to limited fields of view. There are around 40 stars shining between magnitude +5 and +10.

In late May, Melotte III culminates before nightfall but stands tall, around 60 degrees in the south-southwest as the sky darkens. It can be observed throughout the night.

Melotte III is tucked away in the north-west corner of Coma Berenices. AN graphic by Greg Smye-Rumsby.