Although Coma Berenices is a small constellation it does contains one of the densest concentrations of external galaxies in the sky. However its most outstanding feature is not a galaxy but an extremely large and loose naked eye open cluster called Mel 111 or the Coma Star Cluster. In total, Mel 111 contains about 50 stars spread over 6 degrees of apparent size at a distance of 280 light-years.

Although conspicuous and easily visible to the naked eye the cluster was not included in both the Messier or NGC catalogues due to its loose nature, large apparent size and unproven status as a genuine open cluster. It was in 1938 that Swiss-American astronomer Robert J. Trumpler identified 37 stars as cluster members, establishing its true nature. Before that in 1915, British astronomer Philibert J. Melotte included it as number 111 in his catalogue of star clusters, hence the name Melotte 111 or Mel 111.

Melotte 111 The Coma Star Cluster imaged from the International Space Station (ISS) (credit - Donald R. Pettit/NASA)

Finder Chart for Melotte 111 (credit - freestarcharts)

Finder Chart for Melotte 111 - pdf format (credit - freestarcharts)

Mel 111 is located on the southern side of star gamma Com (γ Com - mag. +4.35). This star appears as a cluster member but seems to be a foreground star at 170 light-years distant. The group's brightest stars are all of 5th magnitude, including 12,13,14,16 and 21 Coma Berenices. The Coma Star Cluster is of the finest areas for scanning with binoculars with the brightest stars make out a distinctive "V" shape. With 7x50 models it fits nicely into the field of view (FoV) but with 10x50's it may even over-spill depending on the binocular's apparent FoV. Telescopically it doesn't show much due to their limited fields of view but for binocular observers, this is a gem of an open cluster.

Mel 111 is the second nearest open cluster to the Earth after the Hyades in Taurus (153 light-years). It's best seen from northern latitudes during the months of March, April and May.

Melotte 111 Data Table

Melotte111
Collinder256
NameComa Star Cluster
Object TypeOpen Cluster
ConstellationComa Berenices
Distance (light-years)280
Apparent Mag.1.8
RA (J2000)12h 25m
DEC (J2000)26d 0m
Apparent Size (degrees)6 x 6
Radius (light-years)18
Number of Stars50
Age (years)450 Million
Notable FeatureOne of the nearest star clusters

Sky Highlights - March 2017

Comet
Comet 41P/Tuttle-Giacobini-Kresak now visible with binoculars as it heads towards perihelion

Mercury
Mercury heading towards greatest elongation east

Minor Planet
Vesta now visible with binoculars and small telescopes.

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for March 2017

Northern Hemisphere
Evening
West:- Venus (mag. -4.8 to -4.1 - first half of month), Mars (mag. +1.3 to +1.5), Uranus (mag. +5.9), Mercury (mag. -1.5 to -0.4 - second half of month)
Midnight
Southeast:- Jupiter (mag. -2.3 to -2.5)
Morning
Southwest:- Jupiter
Southeast:- Saturn (mag. +0.5)

Southern Hemisphere
Evening
West:- Venus (first half of month), Mars, Uranus
Midnight
North:- Jupiter
East:- Saturn
Morning
West:- Jupiter
Northeast:- Saturn
East:- Neptune (mag. +8.0 - second half of month)

Deep Sky
Naked eye / binoculars:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)

Telescopes:-
Messier 67 - M67 - Open Cluster
Messier 51 - M51 - The Whirlpool Galaxy (Spiral Galaxy)
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
Messier 101 - M101 - The Pinwheel Galaxy (Spiral Galaxy)
Messier 65 – M65 – Spiral Galaxy
Messier 66 - M66 - Intermediate Spiral Galaxy
Messier 95 - M95 - Barred Spiral Galaxy
Messier 96 - M96 - Intermediate Spiral Galaxy
NGC 4244 - Spiral Galaxy
NGC 4565 - Needle Galaxy - Spiral Galaxy

Shop at Amazon US

Shop at Amazon US

Current Moon Phase

CURRENT MOON

Contributions

If you like the website and want to contribute to the running costs then please do so below. All contributions are most welcome.