Focus On


Focus On Logo


The Coma Berenices star cluster (Melotte 111)



History

The Coma Berenices star cluster, is a large open cluster named after Berenice II, queen of Egypt. She was the daughter of Magas, king of Cyrene.
Around 246 BC Berenice married Ptolemy III, king of Egypt, and became Queen Berenice II. Shortly after they married, Ptolemy set off on a campaign to support his sister in the Third Syrian War.

The legend tells that Berenice vowed to the gods she would offer one of her amber hair locks in the temple of Arsinoe* at Zypherium, if her husband would safely return from his military expedition.

The king returned victorious in 245 BC, and Berenice cut off one of her locks and placed it in the Temple's shrine. The next day the amber hair lock had disappeared. Conon from Samos, a mathematician and astronomer who worked at the court, declared to the king and his wife that the gods had placed the lost hair lock in the heavens. It could be seen as a new constellation between Virgo and Bootes: "Coma Berenice" (Berenice's Hair).


"Coma Berenice” From the Atlas céleste de Flamstéed by John Flamsteed 1776. By courtesy of the National Library of the Netherlands (Koninklijke Bibliotheek)


In 221 BC, shortly after her husband's death, her own son (Ptolemy IV Philopator) had Berenice murdered. The ancient city of Berenice, named after Berenice II by her husband Ptolemy, is still in existence as Benghasi in present-day Libya.

In 1602 Tycho Brahe catalogued Coma Berenices as a separate constellation for the first time. Until then it always had been considered a part of Leo or Virgo. Coma Berenices is the only present-day constellation named after an actual historical person.


Front of Coin

We can find Berenice's portrait on some beautiful gold coins that have been minted during her reign (247 BC - 222 BC). The coin on the left is probably a gold drachm or obol. On the front we see a veiled Berenice. On the back a "Cornucopiae" (the horn of plenty), bound with fillet, between two stars.

Back of coin


Pictures by Courtesy of Penningkabinet, the National Museum of Coins and Medals (Netherlands),
invent.nr. 8770

The National Museum of Coins and Medals



The Constellation Coma Berenices and the Coma Berenices star cluster

The constellation of Coma Berenices is centered between Bootes, Leo, Canes Venatici and Virgo. There are no bright stars in this constellation and in light polluted areas it is almost impossible to locate the constellation with the naked eye. It’s three brightest stars, 42-Alpha (mag.4.3), 43-Beta (mag.4.2) and 15-Gamma (mag.4.3) are barely visible. The constellation contains a globular cluster (M53) and of course there is the large group of galaxies near the southern border, a part of the coma-virgo supercluster.

The Coma Berenices Star Cluster is a large open cluster, covering an area of 5 degrees. In 1938 R.J. Trumpler proved that the Coma star cluster is a true physical cluster. He identified 37 stars as cluster members. It is situated in the north-western part of the constellation Coma Berenices, just a few degrees from the Northern Galactic Pole. This is a peculiar location, because the majority of open clusters can be found in the Milky Way. At a distance of 250 light years, the Coma star cluster is one of the nearest of all the open star clusters. Only the Ursa Major Moving group and the Hyades lie closer to our solar system. Its total mass is about 100 times that of our sun. It contains no giant stars.

The Coma star cluster can be spotted using binoculars, and is best viewed with a 7x50 or 8x56. Moving in a straight line from Denebola (94 Beta-Leonis) to Alkaid (85-Eta Ursae Majoris) you will find the star cluster on one third of this imaginary line, starting from Denebola.

Credit and © Software Bisque, “TheSky for Macintosh”



Although this beautiful star cluster was not included in the NGC or Messier catalogue, it should be on every (binocular) observing list, together with some other large open clusters like M45, The Hyades, and the Alpha Persei Moving Cluster. It culminates at 00.00 (UT) around the first of April and 9 PM (UT) in mid-May. It is best observed during Spring.


Coma star cluster on the web

  • For more information on the Coma Berenices star cluster, click here
  • For a binocular observation log on Melotte 111, please click here

Data Coma star cluster


Common name

Coma Star Cluster

Catalogue-numbers

Melotte 111, Collinder 256

Type/Class

Open Cluster Trumpler Type II 3 p

Magnitude

1.8 (visual)

Number of stars in cluster

80

Brightest star in cluster

Magnitude 4.35 (visual) 15 Gamma Comae Berenices

Size

5 degrees

Distance

288 light Years (Hipparcos)

Radial velocity

-

Age

Estimated at 500 million years

Sky Atlas 2000

Chart 7

RA

12h 25m

Dec

+26°

Constellation

Coma Berenices


Biblography

  • Burnham’s Celestial Handbook, by Robert Burnham JR
  • Binocular Astronomy, by Crossen and Tirion
  • The Night Sky Observer’s Guide, by Kepple and Sanner
  • Woordenboek der Oudheid (Romen, Bussum)
  • Lexicon der Agyptologie (Helck and Otto)
  • Geschichte des Ptolemaerreiches, by Holbl
  • SEDS the Messier Catalogue by Hartmut Frommert
  • Finder chart of constellation Coma Berenices from "TheSky for Macintosh" by Software Bisque


* The mother-in-law of Berenice II was Arsínoe wife of Ptolemy II (283-246BC). She was deified and worshipped as a manifestation of Venus-Aphrodite.



Copyright © 2003 www.backyard-astro.com