Melotte 111

Open Cluster

It seems that back in the day, an astronomer’s claim to fame was the list of objects he created as he explored the heavens, a memoir of sorts. The most famous is Charles Messier’s Catalog that contains 110 M-objects that could easily be mistaken for comets by early comet hunters. Herschel’s list of deep sky objects included 400 objects. I recently read a book by David Levy, a well known, modern day astronomer, comet hunter, science writer that details Levy’s list of deep sky objects.

But I want to introduce you to another list maker, Philibert Jacques Melotte (29 January 1880 – 30 March 1961). Melotte, a British astronomer, is credited with discovering a moon of Jupiter and an asteroid in the asteroid belt. Melotte’s catalog contains 245 open and globular clusters that he discovered while studying photographic plates taken by an astronomer in South Africa and England. One of the characteristics of Melotte’s objects are they are within reach of modest equipment like binoculars and small telescopes.

Melotte 111 is an open star cluster that fills the field of view my 10x50 binoculars. Too big to be recognized as a star cluster in a telescope, its an easy target to find in binoculars if you know where to look. It is located in the constellation of Coma Bernices and is very near the naked eye star gamma Coma Bernices. First, look southeast for Leo the Lion, easily recognized by the big backwards question mark that is dotted by the bright star Regulus. The ‘Sickle’ as the question mark is also called, is the head and mane of Leo. Scan to the left to a triangular group of stars the some astronomers refer to as Leo’s rear-end that includes a bright star called Denebola. Continue scanning left and you’ll find the faint constellation of Coma Bernices that consists of three stars. The highest ( closest to overhead) is gamma. Focus your binoculars on that star and you’ll see the star cluster Mel 111. A string of stars shaped like swirling letter ‘V’ will stretch across your field of view.

My 10 x 50 binoculars has a field of view of 4.5 degrees. The red circle on the star charts shows how much sky I am looking at when I look through my binoculars. Mel 111 fills my field of view. Telescopes have a much smaller field of view because they magnify the image more. My six inch F/8 reflector has a field of view of a little over one degree at its lowest magnification. I would only see a small portion of the cluster at one time and miss the grand view.

Mel 111 is an open cluster of stars that is 250 light years away and contains approximately 36 stars. The bright star Gamma Coma Bernices is not part of the cluster. Astronomers believe the sparse number of stars, so widely spaced, suggests the stars are dispersing.

Also note the time on the star charts. To observe Mel 111 you will have to stay up a little later, 11:00 PM. We are getting into the time of year when the sun stays up longer than we’ve been used to. On April 21 it sets around 7:30 PM. A few hours later Mel 111 rises to a point in the sky for easy viewing.

Brian Cieslak

Horwitz-DeRemer Planetarium

Star charts created using Cartes du Ciel, Binocular image from ‘The Binocular Sky’ website