Coma Berenice header


Coma Berenice star map

Abbreviation: Com

Genitive: Comae Berenices

English: Berenece’s Hair

Size Ranking: 42nd

Area: 386 square degrees

Fully visible 90°N – 55°S.

This faint constellation represents the flowing locks of Queen Berenice of Egypt, who cut off her hair in gratitude to the gods for the safe return of her husband, King Ptolemy III Euergetes, from battle with the Assyrians, and placed her hair in the temple of Venus, from whence Jupiter placed the shining tresses in the sky. Although the legend dates from Greek times, this group of stars was regarded as the tail of Leo until 1551 when the Dutch cartographer Gerardus Mercator made them into a separate constellation. The main part of the Queen’s severed tresses is represented by the extensive Coma Star Cluster.

I suggest that this constellation can be located by finding, Regulus, αLeo, and joining, it with a straight line, to αBoo, Arcturus. αCom is just off this line, approximately one fifth the length of the line out from Arcturus.

Coma Berenices from ancient times was included in the constellations of Leo and Virgo until Tycho Brahe catalogued it as a separate constellation in 1602. The constellation is named in honour of Berenice II of Egypt, Queen of Ptolemy III (246 – 221BC). She sacrificed her blond locks to the gods in the temple of Aphrodite at Zephyrim for the safe return of King Ptolemy III from battle. The offering vanished and the court astronomer Conon convinced the couple the gods had placed the lost trusses into a constellation.

A faint constellation to the naked eye, Coma B. is a telescope rich region of the sky with its many galaxies spreading from the Virgo Cluster of Galaxies to the south. The constellation is bordered on the west by Leo and the east by Bootes, with Virgo to the South.

The three brightest stars are alpha mag. 4.3 a tight binary star 47 ly away, beta mag 4.2 yellow star 30 ly away and gamma 4.4 mag orange giant 170 ly away.

The Coma Star Cluster  (Melotte 111) which represents the hair of Berenice is a scattered open cluster of approximately 40 physically related stars, 288 ly away, one of our closest star clusters. The brightest stars are magnitude 5 and are visible with the naked eye. The cluster is extends south of gamma Com., which is a foreground star not a member of the cluster forming a V. The cluster is best viewed with binoculars.

1 degree northeast of Alpha Comae lies the magnitude 7.5 globular cluster M53 (NGC5024). Visible with binoculars it is quite impressive with a 5 inch telescope, bright and compressed with the edges resolved. With a larger scope it appears as a mass of tiny stars.

1 degree SE of M53 is the unusual globular NGC 5053 which is quite open with loosely scattered stars for a globular cluster. It appears as a hazy patch with an eight inch scope and only larger telescopes will resolve the cluster.

M64 (NGC 4826) The Black Eye Galaxy, a large 8th magnitude oval spiral 1° ENE of 35 Comae is visible with binoculars. This famous galaxy has a dust cloud 40,000 ly in diameter which gives the appearance of a black eye. The dust cloud is visible with a 6 or 8 inch telescope in a clear dark sky. Increase magnification to darken the field and increase the visibility of the “black eye”. Approximately 15 million ly away it is closer to us than the Virgo Cluster of Galaxies.

NGC 4565 the 10th magnitude edge on spiral galaxy, 20 million ly away is another galaxy closer than the Virgo Cluster. A 5 inch scope will show the cigar shape as a bright narrow streak. The central bulge and a dark dust lane will be visible in larger scopes. A spectacular object in photographs – see photo above.

Several galaxies spread from the Virgo Cluster into Coma Berenices forming the Virgo-Coma Galaxy Cluster. The largest of the group M100 (NGC 4321) is a near face on galaxy, 9.5 magnitude 55 million ly away. There may be a hint of the spiral arms with larger scopes. With a 5 inch it will appear as a round glow.

M99 (NGC 4254) “The Pinwheel” mag 9.9, 55 million ly away, another face on spiral appears almost circular. In a dark sky larger than 8 inches will be required to see a hint of the spiral arms.

M85 NGC (4382) mag. 9.1 an elliptical galaxy is visible as an oval mass with a 5 inch scope. M88 (NGC 4501) the multiple armed spiral also appears elliptical, mag. 9.5 M98 (NGC 4192) near edge on mag. 10 spiral galaxy in a small scope has an elongated shape.

M91 (4548) mag 10 barred spiral galaxy appears as a bright round glow in a 5 inch scope. It was described by Messier in 1781 as a nebula without a central star.

With such a multitude of galaxies in this region of the sky it is difficult to determine which you are observing. The best approach is to locate one of the galaxies using your Star Atlas and step from one to the next in a pattern. In a dark sky take time to observe each object and you may be surprised at the detail that becomes visible even in a small telescope. For those of you with goto telescopes this galaxy hopping exercise will be a breeze.

Features of Interest:

αCom, named Diadem, is a tight binary 47 ly away, consisting of twin yellow-white stars of magnitude 5.1 that orbit each other every 26 years. Even at their widest, 0.3”, around the year 2010, they are at the limit of resolution of a 250 mm telescope.

βCom, is a yellow main-sequence  star of magnitude 4.2 and is 30 ly away.

γCom, is an orange giant 170 ly away and of magnitude 4.4. It appears to be a member of the Coma Star Cluster, but is actually a foreground star.

24Com, is a beautiful coloured double star consisting of an orange giant , magnitude 5.0 and 610 ly distant, and an unrelated blue-white companion of magnitude 6.6.

35Com, is a tight binary star consisting of yellow and white components of magnitude 5.1 and 7.2 orbiting every 360 years and are 324 ly away. Telescopes greater than 150 mm aperture are required to split this pair.

Melotte 111, also known as the Coma Star Cluster, is a scattered group of about 50 stars best seen using binoculars. The cluster’s brightest members, of 5th magnitude, form a noticeable V- shape, extending for several degrees south of γCom, which, as mentioned above, is not a member, but a foreground star. The brightest true star is 12Com, magnitude 4.8. The estimated distance to the centre of this cluster is 288 ly.

M53, is an eighth magnitude globular cluster 56,000 ly away, and visible in smaller telescopes as a rounded, hazy patch.


Redshift 2 – Maris Multimedia,  The Guinness Book of Astronomy – Patrick Moore, Stars and Planets – Ian Ridpath and Wil Tirion, Sky Charts – Cartes du Ciel V 2.75., Where the Stars Are – Orion, Collins Stars & Planets 2nd Ed., Ridpath & Tirion;  Deep Sky Companions: The Messier Objects, O’Meara; Deep-Sky Companions: The Caldwell Objects, O’Meara; Hartung’s
Astronomical Objects, 2nd Ed, Malin & Frew; Star Atlas Pro V6.2: Photos from Digital Sky Survey, Burnham’s Celestial Handbook 1966.