Not to be confused with the Coma cluster of galaxies.

The Coma Star Cluster in Coma Berenices

Coma Berenices

Coma Berenices is a traditional asterism that has since been defined as one of the 88 modern constellations. It is located near Leo, to which it formerly belonged, and accommodates the North Galactic Pole...

, designated Melotte 111 after its entry in the catalogue of deep sky objects by P. J. Melotte

Philibert Jacques Melotte

Philibert Jacques Melotte was a British astronomer whose parents immigrated from Belgium.In 1908 he discovered a moon of Jupiter, today known as Pasiphaë. It was simply designated "Jupiter VIII" and was not given its present name until 1975.The asteroid 676 Melitta, the only one he discovered, is...

, is a small but nearby star cluster

Open cluster

An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...

 in our galaxy, containing about 40 brighter stars (magnitude 5 to 10) with a common proper motion

Proper motion

The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...

. The Hipparcos

Hipparcos

Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...

 satellite and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster's center of ~86 pc. The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder

Cosmic distance ladder

The cosmic distance ladder is the succession of methods by which astronomers determine the distances to celestial objects. A real direct distance measurement of an astronomical object is possible only for those objects that are "close enough" to Earth...

. The open cluster is roughly twice as distant as the Hyades

Hyades (star cluster)

The Hyades is the nearest open cluster to the Solar System and one of the best-studied of all star clusters. The Hipparcos satellite, the Hubble Space Telescope, and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster's center of ~153 ly...

 and covers an area of more than 7.5 degrees on the sky. The cluster is approximately 450 million years old. In the FOV of a good field glass most of its stars can be seen simultaneously. The brighter stars of the cluster make out a distinctive "V" shape as seen when Coma Berenices is rising.

It used to represent Leo

Leo (constellation)

Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is . Leo lies between dim Cancer to the west and Virgo to the east.-Stars:...

's tail, but Ptolemy III, in around 240 BC, renamed it for the Egyptian queen Berenice's sacrifice of her hair in a legend.

External links

• WEBDA open cluster database webpage on Coma Ber cluster - E. Pauzen (Univ. Vienna)