Beehive Cluster

The Beehive Cluster is an open cluster in Cancer just visible to the naked eye.
Observation data (J2000.0 epoch)
Constellation	Cancer
Right ascension	08h 40.4m
Declination	19° 59′
Distance	577 ly (177 pc)
Apparent magnitude (V)	3.7
Apparent dimensions (V)	95′
Physical characteristics
Mass	~500-600 M☉
Estimated age	~600-700 million years
Other designations	M44, Praesepe, NGC 2632
See also: Open cluster, List of open clusters

The Beehive Cluster, also known as Praesepe (Latin for "manger"), M44, NGC 2632, or Cr 189, is an open cluster in the constellation Cancer. It is one of the nearest open clusters to the Solar System, and it contains a larger star population than most other nearby clusters. Under dark skies the Beehive Cluster looks like a nebulous object to the naked eye; thus it has been known since ancient times. The classical astronomer Ptolemy called it "the nebulous mass in the breast of Cancer," and it was among the first objects that Galileo studied with his telescope.

The cluster's age and proper motion coincide with those of the Hyades open cluster, suggesting that both share a similar origin. Both clusters also contain red giants and white dwarfs, which represent later stages of stellar evolution, along with main sequence stars of spectral classes A, F, G, K, and M.

The cluster's distance is often cited to lie between 160 and 187 parsecs (520-610 light years). The 2009 catalog of revised Hipparcos parallaxes for Praesepe members and the latest iteration of color-magnitude diagram fitting in the infrared favor an analogous distance near 182 pc. There is better agreement on its age, at about 600 million years. This is equivalent to the age of the Hyades (~625 million years). The bright central core of the cluster has a diameter of about 7 parsecs (22.8 light years).

The Beehive is most easily observed when Cancer is high in the sky; in northern latitudes this occurs during the evening from February to May. At 95 arcminutes across, the cluster fits well in the field of view of a pair of binoculars or a telescope of low power.

Galileo was the first to observe the Beehive in a telescope, in 1609, and was able to resolve it into 40 stars. Charles Messier added it to his famous catalog in 1769 after precisely measuring its position in the sky. Along with the Orion Nebula and the Pleiades cluster, Messier's inclusion of the Beehive has been noted as curious, as most of Messier's objects were much fainter and more easily confused with comets. One possibility is that Messier simply wanted to have a larger catalog than his scientific rival Lacaille, whose 1755 catalog contained 42 objects, and so he added some bright, well-known objects to boost his list.