Coma Berenices

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Coma Berenices
Coma Berenices
Abbreviation Com
Genitive Comae Berenices
Pronunciation /ˈkmə bɛrəˈnsz/,
genitive /ˈkm/
Symbolism Berenice's hair
Right ascension 11h 58m 25.0885s–13h 36m 06.9433s[1]
Declination 33.3074303°–13.3040485°[1]
Family Ursa Major
Area 386 sq. deg. (42nd)
Main stars 3
Stars with planets 5
Stars brighter than 3.00m 0
Stars within 10.00 pc (32.62 ly) 1
Brightest star β Com (4.26m)
Nearest star β Com
(29.96 ly, 9.18 pc)
Messier objects 8
Meteor showers Coma Berenicids
Canes Venatici
Ursa Major
Visible at latitudes between +90° and −70°.
Best visible at 21:00 (9 p.m.) during the month of May.

Coma Berenices is an ancient asterism that has since been defined as one of the 88 modern constellations. It is located in the fourth galactic quadrant, between Leo and Bootes, and is visible in both celestial hemispheres. Introduced to the Western astronomy in the 3rd century BC by Conon of Samos, its name means "Berenice's Hair" (in Greek, via Latin), referring to Queen Berenice II of Egypt, who sacrificed her long hair as a votive offering.

Three stars of Coma Berenices visible to the naked eye form a 45-degree isosceles triangle. The constellation's brightest star is Beta Comae Berenices, a 4.26-magnitude main sequence star, similar to Sun. Coma Berenices contains one of the richest known galaxy clusters, the Coma Cluster, and the North Galactic Pole. The brightest known supernova, SN 2005ap was detected in Coma Berenices. The constellation is the radiant of one meteor shower, Coma Berenicids which has one of the fastest meteor speeds, up to 65 km/s (40 mps).


A fragment of Mercator's celestial globe showing Coma Berenices under five names, 1551.

Coma Berenices has been recognized as a distinct asterism since the Hellenistic period[2] (according to some authors, much earlier) and is the only modern constellation named after a historical person. It was introduced to the Western astronomy in the 3rd century BC by Conon of Samos, court astronomer to Egyptian ruler Ptolemy III Euergetes, to honour Ptolemy's consort, Berenice II.[3] Berenice vowed to sacrifice her long hair in a votive offering, if Ptolemy returned safely from a battle during the Third Syrian War.[4] Modern scholars are uncertain whether Berenice made the sacrifice before or after Ptolemy's return; it was suggested that it happened after Ptolemy's return around March–June 245 BC when Conon presented the asterism jointly with scholar and poet Callimachus.[5] In Callimachus' poem Aetia, composed around that time, Berenice dedicated her tresses "to all the gods", while in the Latin translation of the poem by Roman poet Catullus and in Hyginus' De astronomica she dedicated the tresses to Aphrodite, placing them in the temple of Arsinoe II (identified, after her death, with Aphrodite) at Zephyrium. According to De astronomica, by the next morning the tresses have disappeared. Conon proposed that Aphrodite had interceded to place the tresses in the sky as an acknowledgement of Berenice's sacrifice.[4] Callimachus called the asterism πλόκαμος Βερενίκης or βόστρυχον Βερενίκης which was later rendered in Latin as Coma Berenices by Catullus.

The asterism was also recognized in its own right by Greek astronomers Geminus[6] and Eratosthenes, the latter referred to it as both "Ariadne's Hair" and "Berenice's Hair". Ptolemy referred to it as "the lock" of hair; however, he did not list it as one of his 48 constellations, considering it to be a part of Leo,[2] specifically, the tuft at the end of the tail.

Coma Berenices gained new popularity in the 16th century. In 1515, a set of gores made by Johannes Schöner labelled the asterism as "Trica" ("hair"). In 1536 it appeared on a celestial globe by the cartographer Caspar Vopel[7] who is often credited with the asterism's elevation to constellation status. In 1551, Coma Berenices appeared on a celestial globe by Gerardus Mercator under five Latin and Greek names (Cincinnus, caesaries, πλόκαμος, Berenicis crinis and Trica). Mercator's authority as a cartographer ensured the continuous representation of Coma Berenices on Dutch globes from 1589 onwards.[8]

Tycho Brahe, who is also given credit for Coma's promotion to constellation status, listed it in his star catalogue of 1602.[2] Brahe recorded fourteen stars in the constellation, Johannes Hevelius increased this number to twenty-one and John Flamsteed to forty-three. Coma Berenices also appeared in Johann Bayer's Uranometria of 1603, and during the 17th century, a few other celestial maps followed suit. Coma Berenices and the now-obsolete constellation Antinous are considered to be the first post-Ptolemaic constellations to be depicted on a celestial globe.[9] Alongside Antinous, Coma Berenices exemplified a trend in astronomy when globe- and map-makers continued to rely on the ancients for new data. The trend would end at the turn of the 16th century by the explorations of the southern sky and the work of Tycho Brahe.[8]

In English, before the 18th century Coma Berenices was known under different names, such as Berenice's Bush and Berenice's periwig.[10] The earliest known English name, Berenices haire (Berenices Hair) comes from 1601.[11][10] By 1702 the constellation was already called Coma Berenices[12] and was referred to as such in An Universal Etymological English Dictionary from 1731.

Non-Western astronomy[edit]

It was suggested that Coma Berenices was known already to the Akkadians as ḪE2.GAL2.LA.[13] In the Babylonian astronomy, a star called ḪÉ.GÁL-a-a (translated as "which is before it") or MÚL.ḪÉ.GÁL-a-a is putatively considered part of Coma Berenices.[14] It was argued that Coma Berenices also appears in the Egyptian Ramesside star charts as sb3w ꜥš3w, meaning "Many Stars".[15]

In the Arabian astronomy, Coma Berenices was known as Al-Hulba and Al-Ḍafīra.

In Chinese astronomy, the stars of Coma Berenices are located in two areas: the Supreme Palace enclosure and the Azure Dragon of the East. Several stars in the constellation had their own Chinese names.

Indigenous Pawnee people from North America putatively depicted Coma Berenices as ten faint stars on their star map dated to at least 17th century and made from tanned elk skin.[16] The constellation also occupies an important place in the beliefs of South American Kalina people where it was called ombatapo, meaning "face".[17] In the area inhabited by the Kalina, Coma Berenices becomes visible in October.[17]

Coma Berenices was recognized by several Polynesian peoples. The people of the Pukapuka atoll likely called it Te Yiku-o-te-kiole; the people of Tonga had three different names. These included Fatana-lua, Fata-olunga (also Fata-lalo), and Kapakau-o-Tafahi.[18] The Boorong people called the constellation Tourt-chinboiong-gherra, seeing it as a small bird flock drinking rainwater from a small puddle in the tree fork.[19]

Notable features[edit]

The constellation Coma Berenices as seen by the naked eye.

Coma Berenices is entirely visible north of the 56th parallel south.[20] The constellation's visibility culminates on 2 April at midnight.[21] Although it is not a large constellation, it contains two galactic clusters, one star cluster and eight Messier objects, including several globular clusters. These objects can be seen with minimal obscuration from dust because the constellation is not in the direction of the galactic plane. However, because of this fact, there are few open clusters (except for the Coma Berenices Cluster, which dominates the northern part of the constellation), diffuse nebulae, or planetary nebulae. Coma Berenices also contains the North Galactic Pole, at right ascension 12h 51m 25s and declination +27° 07′ 48″ (epoch J2000.0).


Further information: List of stars in Coma Berenices

Coma Berenices is not particularly bright, having no stars brighter than fourth magnitude, but in clear, moonless nights there are up to fifty stars visible to the naked eye.[22] Beta Comae Berenices is the brightest star in the constellation, at magnitude 4.2; it is 30 light-years from Earth. Like the Sun, it is a yellow-hued main-sequence star.[23] It is intrinsically only slightly brighter than the Sun, which gives an idea of how faint the Sun would appear seen from Beta Comae's distance.

The second brightest star in Coma Berenices is Alpha Comae Berenices, with the proper name Diadem. The name represents the gem in Berenice's crown.[24] It is a binary star, with two components of almost equal magnitude. It has an apparent magnitude of 4.3.[23] Because the orbital plane is so close to the Earth's line of sight, it was long suspected of being an eclipsing binary, but it now appears that the orbital tilt is 0.1° relative to the line of sight, so the stars do not eclipse each other as seen from Earth.[24] The two components are slightly yellow-tinged; both are of magnitude 5.1. This binary has a period of 26 years and is 47 light-years from Earth.[23]

Photo of major stars in Coma Berenices.

Gamma Comae Berenices, which is superimposed on the Coma Star Cluster, is an orange-hued giant star of magnitude 4.4, 170 light-years from Earth. Together with Alpha Comae Berenices and Beta Comae Berenices, it forms an imaginary inverted L-shaped support, from which the imaginary tresses of Berenice hang. They are delineated by fainter Flamsteed-designated stars.

There are two prominent star systems in Coma Berenices. 35 Comae Berenices is a binary star with an optical companion. The two physically related components have a period of 360 years and are 324 light-years from Earth. The primary is a yellow-hued star of magnitude 5.1 and the secondary is a white-hued star of magnitude 7.2. The optical tertiary component is of magnitude 9. 24 Comae Berenices is a double star with contrasting colors. The primary is an orange-hued giant star of magnitude 5.0, 610 light-years from Earth, and the secondary is a blue-white hued star of magnitude 6.6.[23]

Over 200 variable stars are known in Coma Berenices, although many of them are obscure. FK Comae Berenices, which varies between 8.14m and 8.33m over a period of 2.4 days, is the prototype for the FK Com class of variable stars. It is believed that the variability of FK Com stars is caused by large, cool spots on the rotating surfaces of the stars. FS Comae Berenices is a semi-regular variable, a red giant with a minimum magnitude of 6.1 and a maximum magnitude of 5.3. It has a period of approximately 2 months and is 572 light-years from Earth.[23]

In 2005, the brightest known supernova, SN 2005ap was detected in Coma Berenices. Due to great distance (4.7 billion light years from Earth) it was not visible to the naked eye and was discovered telescopically. The constellation also contains the neutron star RBS 1223 and pulsar PSR B1237+25.[25]

Star clusters[edit]

Coma Star Cluster[edit]

Main article: Coma Star Cluster

The Coma Star Cluster does not have a Messier or an NGC designation, but it is in the Melotte catalogue of open clusters, where it is designated Melotte 111, and is also catalogued as Abell 1656. It is a large, diffuse open cluster of about 50 stars that range between 5th and 10th magnitudes, including several of the naked eye stars in the constellation. 12 Comae Berenices, at magnitude 4.8, is the cluster's brightest member. The cluster is spread over a huge region, more than 5 degrees across, near γ Coma Berenices. The cluster has such a large apparent size because it is relatively nearby, only 288 light years away.[23]

Globular clusters[edit]

M53 (NGC 5024) is a globular cluster that was discovered by Johann Elert Bode in 1775 and independently by Charles Messier in February 1777. It is of magnitude 7.7 and is 56,000 light-years from Earth. M53 is a Shapley class V cluster, indicating that it has intermediate concentration towards its center. Only 1° away is NGC 5053,[26] a globular cluster that is sparser and has a less dense nucleus of stars. Its total luminosity is around 16,000 suns, which is one of the lowest luminosities of any globular cluster. It was discovered by William Herschel in 1784. It is around magnitude 9.9 m. NGC 4147 is a somewhat dimmer (magnitude 10.2m) globular cluster with a much smaller apparent size.


NGC 4565 has been nicknamed the Needle Galaxy because, when seen in full, it appears as a very narrow streak of light on the sky.[27]

Coma Cluster[edit]

Main article: Coma Cluster

The Coma cluster of galaxies is to the north of the Virgo Cluster. It lies much further off, however, around 230 to 300 million light years away.[23] The cluster is quite large, containing 1,000 large galaxies and possibly up to 30,000 smaller ones. A survey by Fritz Zwicky in 1957 identified 29,951 galaxies in the area that are brighter than 19.0m. While some of these may be distant background objects, the total number of galaxies in the cluster is quite large.

Due to the great distance to the cluster, most of the galaxies are only visible in large telescopes. The brightest members are NGC 4889 and NGC 4874, both of which are of thirteenth magnitude, with most of the other members being of fifteenth magnitude or dimmer. NGC 4889 is a giant elliptical galaxy, which is also the home of the largest known black hole at 21 billion solar masses.[28] The Coma cluster contains comparatively few spiral galaxies. NGC 4921 is the brightest among them.[29]

Coma–Virgo Cluster[edit]

Main article: Virgo Cluster

Coma Berenices contains the northern portion of the Virgo cluster (also known as the Coma-Virgo cluster), which is around 60 million light years away.

M100 (NGC 4321) is a 9th-magnitude spiral galaxy seen face-on. It is part of the Virgo Cluster.[23] At 7 arcminutes across, it has the largest apparent size of any galaxy in the Virgo cluster. Its diameter is over 120,000 light years, making it among the largest spiral galaxies in the Virgo cluster. Photographs reveal a brilliant core, two prominent spiral arms and an array of secondary ones, as well as several dust lanes.

M85 (NGC 4382) is an elliptical galaxy in the Virgo cluster. It is one of the brighter members of the cluster at magnitude 9. Its nucleus is bright and appears starlike in small amateur telescopes.[23] M85 is interacting with spiral galaxy NGC 4394 and the elliptical galaxy MCG-3-32-38.[25]

M88 (NGC 4501) is a multi-arm spiral galaxy, seen about 30° from edge-on. The galaxy has a supermassive black hole in its center.[25]

M91 (NGC 4548) is a barred spiral galaxy with bright, diffuse nucleus.

M98 (NGC 4192) is a bright, elongated spiral galaxy that is seen nearly edge-on; it can appear elliptical because of its unusual angle. It is of the 10th magnitude and is a member of the Virgo Cluster.

M99 (NGC 4254) is a spiral galaxy seen face-on. Like M98, it is a 10th-magnitude member of the Virgo Cluster. R.H. Allen called it the "Pinwheel nebula", although this name is more often applied to the Triangulum Galaxy.

Other galaxies[edit]

M64, the Black Eye Galaxy

M64 (NGC 4826) is known as the Black Eye Galaxy because of the prominent dark dust lane in front of the galaxy's bright nucleus. The dust lane is only visible in larger amateur telescopes, though galaxy is easily visible in even the smallest amateur instruments because it is of the 9th magnitude.[23] Also known as the Sleeping Beauty and Evil Eye galaxy, it is relatively nearby, at around 17 million light years away from Earth. Recent studies have revealed that the interstellar gas in the outer regions of the galaxy rotates in the opposite direction from that in the inner regions, leading astronomers to believe that at least one satellite galaxy had collided with it less than a billion years ago. All other evidence of the smaller galaxy has been destroyed; it has been completely assimilated. At the interface between the clockwise- and counterclockwise- rotating regions, there are many new nebulae and young stars.[30]

NGC 4565, the Needle galaxy

NGC 4314 is a face-on barred spiral galaxy at a distance of 40 million light-years. It is unique for its region of intense star formation that creates a ring around the nucleus, discovered by the Hubble Space Telescope. The prodigious star formation began a short 5 million years ago and is in a region with a diameter of only 1,000 light-years. The architecture of the core is further unique because the small ring itself has spiral arms that feed gas into the bar.[30]

NGC 4414 is an unbarred spiral flocculent galaxy located about 62 million light-years away.

NGC 4565 is a very well known edge-on spiral galaxy. It is of the 10th magnitude and appears superimposed on the Virgo Cluster, though it is only 20 million light-years from Earth. Like many edge-on spiral galaxies, it has a prominent dust lane and a central bulge.[23]

NGC 4676, sometimes called the "Mice" galaxies, is a pair of interacting galaxies at a distance of 300 million light-years from Earth. The progenitor galaxies were both spiral galaxies; astronomers estimate that they had their closest approach about 160 million years ago. That close approach caused large regions of star formation in both galaxies, along with long "tails" of dust, stars, and gas. The two progenitor galaxies are predicted to interact significantly at least one more time before completely merging into a larger, probably elliptical galaxy.[30]


Coma Berenices contains three known exoplanets: HD 108874 b, HD 108874 c and HD 114762 b.[31] HD 108874 b has a close Earth-like insolation.[31]


Quasar PG1247+26° is the brightest quasar visible in Coma Berenices. As well, W Com was originally identified as a variable star and so given a variable star designation, but later discovered to be a BL Lacertae object. It is normally around magnitude 16.5 m, but has been known to reach 12th magnitude.

Meteor shower[edit]

The December Coma Berenicids are a meteor shower that lasts from December through January; it peaks between December 18 and 25.[32] Despite slow intensity (one or two meteors per hour on average), its meteors are one of the fastest, with speeds of up to 65 km/s (40 mps).[33]


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External links[edit]

Coordinates: Sky map 12h 45m 36s, +21° 49′ 48″