Beehive Cluster
Encyclopedia
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 to 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.
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.
Ancient Greeks and Romans saw this object as a manger from which two donkeys, the adjacent stars Asellus Borealis
and Asellus Australis
, are eating; these are the donkeys that Dionysos and Silenus
rode into battle against the Titans
.
This perceived nebulous object is the main celestial object in the 23rd lunar mansion (Hsiu Kuei or Xiu Gui) of ancient Chinese astrology. Ancient Chinese skywatchers saw this as a ghost or demon riding in a carriage and likened its appearance to a "cloud of pollen blown from willow catkins."
. This means that bright, massive stars are concentrated in the cluster's core, while dimmer, less massive stars populate its halo (sometimes called the "corona"). The cluster's core radius is estimated at 3.5 parsecs (11.4 light years); its half-mass radius is about 3.9 parsecs (12.7 light years); and its tidal radius is about 12 parsecs (39 light years). However, the tidal radius also includes many stars that are merely "passing through" and not bona fide cluster members.
Altogether, the Praesepe cluster contains at least 1000 gravitationally bound stars, for a total mass of about 500-600 Solar masses. A recent survey counts 1010 high-probability members, of which 68% are M dwarfs
, 30% are Sun-like stars of spectral classes F, G, and K, and about 2% are bright stars of spectral class A. Also present are five giant stars, four of which have spectral class K0 III and the fifth G0 III.
So far, eleven white dwarfs have been identified, representing the final evolutionary phase of the cluster's most massive stars, which originally belonged to spectral type B. Brown dwarfs, however, are extremely rare in this cluster, probably because they have been lost by tidal stripping from the halo.
The cluster has a visual brightness of magnitude 3.7. Its brightest stars are blue-white and of magnitude 6 to 6.5. 42 Cancri
is a confirmed member.
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 the constellation Cancer
Cancer (constellation)
Cancer is one of the twelve constellations of the zodiac. Its name is Latin for crab and it is commonly represented as such. Its symbol is . Cancer is small and its stars are faint...
. It is one of the nearest open clusters to the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
, 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
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
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
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...
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
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
stars of spectral classes A, F, G, K, and M.
The cluster's distance is often cited to lie between 160 to 187 parsecs (520-610 light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....
). The 2009 catalog of revised 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...
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.
History
Galileo was the first to observe the Beehive in a telescope, in 1609, and was able to resolve it into 40 stars. Charles MessierCharles Messier
Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 110 "Messier objects"...
added it to his famous catalog
Messier object
The Messier objects are a set of astronomical objects first listed by French astronomer Charles Messier in 1771. The original motivation of the catalogue was that Messier was a comet hunter, and was frustrated by objects which resembled but were not comets...
in 1769 after precisely measuring its position in the sky. Along with the Orion Nebula
Orion Nebula
The Orion Nebula is a diffuse nebula situated south of Orion's Belt. It is one of the brightest nebulae, and is visible to the naked eye in the night sky. M42 is located at a distance of and is the closest region of massive star formation to Earth. The M42 nebula is estimated to be 24 light...
and the Pleiades
Pleiades (star cluster)
In astronomy, the Pleiades, or Seven Sisters , is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky...
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
Nicolas Louis de Lacaille
Abbé Nicolas Louis de Lacaille was a French astronomer.He is noted for his catalogue of nearly 10,000 southern stars, including 42 nebulous objects. This catalogue, called Coelum Australe Stelliferum, was published posthumously in 1763. It introduced 14 new constellations which have since become...
, whose 1755 catalog contained 42 objects, and so he added some bright, well-known objects to boost his list.
Ancient Greeks and Romans saw this object as a manger from which two donkeys, the adjacent stars Asellus Borealis
Gamma Cancri
Gamma Cancri is a star system in the constellation Cancer. It has the traditional name Asellus Borealis ....
and Asellus Australis
Delta Cancri
Delta Cancri is an orange giant star approximately 180 light-years away in the constellation Cancer. It has the traditional name Asellus Australis which in Latin means "southern donkey colt"...
, are eating; these are the donkeys that Dionysos and Silenus
Silenus
In Greek mythology, Silenus was a companion and tutor to the wine god Dionysus.-Evolution of the character:The original Silenus resembled a folklore man of the forest with the ears of a horse and sometimes also the tail and legs of a horse...
rode into battle against the Titans
Titan (mythology)
In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, that ruled during the legendary Golden Age....
.
This perceived nebulous object is the main celestial object in the 23rd lunar mansion (Hsiu Kuei or Xiu Gui) of ancient Chinese astrology. Ancient Chinese skywatchers saw this as a ghost or demon riding in a carriage and likened its appearance to a "cloud of pollen blown from willow catkins."
Morphology and composition
Like many star clusters of all kinds, Praesepe has experienced mass segregationMass segregation
In astronomy, dynamical mass segregation is the process by which heavier members of a gravitationally bound system, such as a star cluster or cluster of galaxies, tend to move toward the center, while lighter members tend to move farther away from the center. Primordial mass segregation is...
. This means that bright, massive stars are concentrated in the cluster's core, while dimmer, less massive stars populate its halo (sometimes called the "corona"). The cluster's core radius is estimated at 3.5 parsecs (11.4 light years); its half-mass radius is about 3.9 parsecs (12.7 light years); and its tidal radius is about 12 parsecs (39 light years). However, the tidal radius also includes many stars that are merely "passing through" and not bona fide cluster members.
Altogether, the Praesepe cluster contains at least 1000 gravitationally bound stars, for a total mass of about 500-600 Solar masses. A recent survey counts 1010 high-probability members, of which 68% are M dwarfs
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
, 30% are Sun-like stars of spectral classes F, G, and K, and about 2% are bright stars of spectral class A. Also present are five giant stars, four of which have spectral class K0 III and the fifth G0 III.
So far, eleven white dwarfs have been identified, representing the final evolutionary phase of the cluster's most massive stars, which originally belonged to spectral type B. Brown dwarfs, however, are extremely rare in this cluster, probably because they have been lost by tidal stripping from the halo.
The cluster has a visual brightness of magnitude 3.7. Its brightest stars are blue-white and of magnitude 6 to 6.5. 42 Cancri
42 Cancri
42 Cancri is a star in the constellation Cancer. Its apparent magnitude is 6.83.42 Cancri is a member of the Beehive Cluster....
is a confirmed member.
See also
- Messier objectMessier objectThe Messier objects are a set of astronomical objects first listed by French astronomer Charles Messier in 1771. The original motivation of the catalogue was that Messier was a comet hunter, and was frustrated by objects which resembled but were not comets...
- List of Messier objects
- List of open clusters
- New General CatalogueNew General CatalogueThe New General Catalogue of Nebulae and Clusters of Stars is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects...