Coma Berenices
Coma Berenices is an ancient asterism in the northern sky, which has been defined as one of the 88 modern constellations. It is in the direction of the fourth galactic quadrant, between Leo and Boötes, and it is visible in both hemispheres. Its name means "Berenice's Hair" in Latin and refers to Queen Berenice II of Egypt, who sacrificed her long hair as a votive offering. It was introduced to Western astronomy during the third century BC by Conon of Samos and was further corroborated as a constellation by Gerardus Mercator and Tycho Brahe. It is the only modern constellation named after a historic person.
The constellation's major stars are Alpha, Beta, and Gamma Comae Berenices. They form a half square, along the diagonal of which run Berenice's imaginary tresses, formed by the Coma Star Cluster. The constellation's brightest star is Beta Comae Berenices, a 4.2-magnitude main sequence star similar to the Sun. Coma Berenices contains the North Galactic Pole and one of the richest-known galaxy clusters, the Coma Cluster, part of the Coma Supercluster. Galaxy Malin 1, in the constellation, is the first-known giant low-surface-brightness galaxy. Supernova SN 1940B was the first scientifically observed type II supernova. FK Comae Berenices is the prototype of an eponymous class of variable stars. The constellation is the radiant of one meteor shower, Coma Berenicids, which has one of the fastest meteor speeds, up to.
History
Coma Berenices has been recognized as an asterism since the Hellenistic period, and is the only modern constellation named for an historic figure. It was introduced to Western astronomy during the third century BC by Conon of Samos, the court astronomer of Egyptian ruler Ptolemy III Euergetes, to honour Ptolemy's consort, Berenice II. Berenice vowed to sacrifice her long hair as a votive offering if Ptolemy returned safely from battle during the Third Syrian War. Modern scholars are uncertain if Berenice made the sacrifice before or after Ptolemy's return; it was suggested that it happened after Ptolemy's return, when Conon presented the asterism jointly with scholar and poet Callimachus during a public evening ceremony. In Callimachus' poem, Aetia, Berenice dedicated her tresses "to all the gods". In Poem 66, the Latin translation by the Roman poet Catullus, and in Hyginus' De Astronomica, she dedicated her tresses to Aphrodite and placed them in the temple of Arsinoe II at Zephyrium. According to De astronomica, by the next morning the tresses had disappeared. Conon proposed that Aphrodite had placed the tresses in the sky as an acknowledgement of Berenice's sacrifice. Callimachus called the asterism plokamos Berenikēs or bostrukhon Berenikēs in Greek, translated into Latin as "Coma Berenices" by Catullus. Hipparchus and Geminus also recognized it as a distinct constellation. Eratosthenes called it "Berenice's Hair" and "Ariadne's Hair", considering it part of the constellation Leo. Similarly, Ptolemy did not include it among his 48 constellations in the Almagest; considering it part of Leo and calling it Plokamos.Image:Virgo et Coma Berenices - Mercator.jpeg|thumb|left|180px|alt=Sixteenth-century sky map superimposed on a globe|Coma Berenices on Mercator's 1551 celestial globe, in the upper left
Coma Berenices became popular during the 16th century. In 1515, a set of gores by Johannes Schöner labelled the asterism Trica, "hair". In 1536 it appeared on a celestial globe by Caspar Vopel, who is credited with the asterism's designation as a constellation. That year, it also appeared on a celestial map by Petrus Apianus as "Crines Berenices". In 1551, Coma Berenices appeared on a celestial globe by Gerardus Mercator with five Latin and Greek names: Cincinnus, caesaries, πλόκαμος, Berenicis crinis and Trica. Mercator's reputation as a cartographer ensured the constellation's inclusion on Dutch sky globes beginning in 1589.
Tycho Brahe, also credited with Coma's designation as a constellation, included it in his 1602 star catalogue. Brahe recorded fourteen stars in the constellation; Johannes Hevelius increased its number to twenty-one, and John Flamsteed to forty-three. Coma Berenices also appeared in Johann Bayer's 1603 Uranometria, and a few other 17th-century celestial maps followed suit. Coma Berenices and the now-obsolete Antinous are considered the first post-Ptolemaic constellations depicted on a celestial globe. With Antinous, Coma Berenices exemplified a trend in astronomy in which globe- and map-makers continued to rely on the ancients for data. This trend ended at the turn of the 16th century with observations of the southern sky and the work of Tycho Brahe.
Before the 18th century Coma Berenices was known in English by several names, including "Berenice's Bush" and "Berenice's periwig". The earliest-known English name, "Berenices haire", dates to 1601. By 1702 the constellation was known as Coma Berenices, and appears as such in the 1731 Universal Etymological English Dictionary.
Non-Western astronomy
Coma Berenices was known to the Akkadians as Ḫegala. In Babylonian astronomy a star, known as ḪÉ.GÁL-a-''a or MÚL.ḪÉ.GÁL-a''-a, is tentatively considered part of Coma Berenices. It was also argued that Coma Berenices appears in Egyptian Ramesside star clocks as sb3w ꜥš3w, meaning "many stars".In Arabic astronomy Coma Berenices was known as Al-Dafira الضفيرة, ''Al-Hulba الهلبة and Al-Thu'aba الذؤابة, the latter two are translations of the Ptolemaic Plokamos, forming the tuft of the constellation Leo and including most of the Flamsteed-designated stars. Al-Sufi included it in Leo. Ulugh Beg, however, regarded Al-Dafira as consisting of two stars, 7 and 23 Comae Berenices. R. H. Allen's Star Names gives the name Al Ḍafīrah to 15 = Gamma Comae Berenices.
The North American Pawnee people depicted Coma Berenices as ten faint stars on a tanned elk-skin star map dated to at least the 17th century. In the South American Kalina mythology, the constellation was known as ombatapo.
The constellation was also recognized by several Polynesian peoples. The people of Tonga had four names for Coma Berenices: Fatana-lua, Fata-olunga, Fata-lalo and Kapakau-o-Tafahi. The Boorong people called the constellation Tourt-chinboiong-gherra, and saw it as a small flock of birds drinking rainwater from a puddle in the crotch of a tree. The people of the Pukapuka atoll may have called it Te Yiku-o-te-kiole'', although sometimes this name is associated with Ursa Major.
Characteristics
Coma Berenices is bordered by Boötes to the east, Canes Venatici to the north, Leo to the west and Virgo to the south. Covering 386.5 square degrees and 0.937% of the night sky, it ranks 42nd of the 88 constellations by area. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Com". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 12 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between and, and the declination coordinates are between +13.30° and +33.31°. Coma Berenices is wholly visible to observers north of latitude 56°S. and the constellation's midnight culmination occurs on 2 April.Features
Although it is not large, Coma Berenices contains one galactic supercluster, two galactic clusters, one star cluster and eight Messier objects. These objects can be seen with minimal obscuration by dust because the constellation is not in the direction of the galactic plane. Because of that, there are few open clusters, diffuse nebulae or planetary nebulae. Coma Berenices contains the North Galactic Pole at right ascension and declination .Stars
Brightest stars
Coma Berenices is not particularly bright, as none of its stars are brighter than fourth magnitude, although there are 66 stars brighter than or equal to apparent magnitude 6.5.The constellation's brightest star is Beta Comae Berenices, at magnitude 4.2 and with a high proper motion. In Coma Berenices' northeastern region, it is 29.95 ± 0.10 light-years from Earth. A solar analog, it is a yellow-hued F-type main-sequence star with a spectral class of F9.5V B. Beta Comae Berenices is around 36% brighter, and 15% more massive than the Sun, and with a radius 10% larger.
The second-brightest star in Coma Berenices is the 4.3-magnitude, bluish Alpha Comae Berenices, with the proper name Diadem, in the southeastern part of the constellation. Despite its Alpha Bayer designation, the star is dimmer than Beta Comae Berenices, being one of the cases where designation does not correspond to the brightest star. It is a double star, with the spectral classes of F5V and F6V. The star system is 58.1 ± 0.9 light-years from Earth.
Gamma Comae Berenices is an orange-hued giant star with a magnitude of 4.4 and a spectral class of K1III C. In the southwestern part of the constellation, it is 169 ± 2 light-years from Earth, Estimated to be around 1.79 times as massive as the Sun, it has expanded to around 10 times its radius. It is the brightest star in the Coma Star Cluster. With Alpha Comae Berenices and Beta Comae Berenices, Gamma Comae Berenices forms a 45-degree isosceles triangle from which Berenice's imaginary tresses hang.
Star systems
The star systems of Coma Berenices include binary, double and triple stars. 21 Comae Berenices is a close binary with nearly equal components and an orbital period of 26 years. The system is 272 ± 3 light-years away. The Coma Cluster contains at least eight spectroscopic binaries, and the constellation has seven eclipsing binaries: CC, DD, EK, RW, RZ, SS and UX Comae Berenices.There are over thirty double stars in Coma Berenices, including 24 Comae Berenices with contrasting colors. Its primary is an orange-hued giant star with a magnitude of 5.0, 610 light-years from Earth, and its secondary is a blue-white-hued star with a magnitude of 6.6. Triple stars include 12 Comae Berenices, 17 Comae Berenices, KR Comae Berenices and Struve 1639.