Canes Venatici as depicted in Hevelius's star atlas. Note that, per the conventions of the time, the image is mirrored.Canes Venatici can be seen in the orientation it appears to the eyes in this 1825 star chart from Urania's Mirror.
The stars of Canes Venatici are not bright. In classical times, they were listed by Ptolemy as unfigured stars below the constellation Ursa Major in his star catalogue.
In medieval times, the identification of these stars with the dogs of Boötes arose through a mistranslation: some of Boötes's stars were traditionally described as representing the club (Greek: κολλοροβος, kollorobos) of Boötes. When the Greek astronomer Ptolemy's Almagest was translated from Greek to Arabic, the translator Hunayn ibn Ishaq did not know the Greek word and rendered it as a similar-sounding compound Arabic word for a kind of weapon, writing العصا ذات الكُلابal-'aşā dhāt al-kullāb, which means 'the staff having a hook'.
When the Arabic text was later translated into Latin, the translator, Gerard of Cremona, mistook كُلابkullāb ('hook') for كِلابkilāb ('dogs'). Both written words look the same in Arabic text without diacritics, leading Gerard to write it as Hastile habens canes ('spearshaft-having dogs').[3]
In 1533, the German astronomer Peter Apian depicted Boötes as having two dogs with him.[4]
These spurious dogs floated about the astronomical literature until Hevelius decided to make them a separate constellation in 1687.[5] Hevelius chose the name Asterion[a] for the northern dog and Chara[b] for the southern dog, as Canes Venatici, 'the hunting dogs', in his star atlas.[7]
In his star catalogue, the Czech astronomer Antonín Bečvář assigned the names Asterion to β CVn and Chara to α CVn.[8]
Canes Venatici is bordered by Ursa Major to the north and west, Coma Berenices to the south, and Boötes to the east. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "CVn".[10] The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930,[9] are defined by a polygon of 14 sides.
In the equatorial coordinate system, the right ascension coordinates of these borders lie between 12h 06.2m and 14h 07.3m, while the declination coordinates are between +27.84° and +52.36°.[2] Covering 465 square degrees, it ranks 38th of the 88 constellations in size.
Prominent stars and deep-sky objects
The constellation Canes Venatici as it is seen by the naked eye in twilight
Canes Venatici contains no very bright stars. The Bayer designation stars, Alpha and Beta Canum Venaticorum are only of third and fourth magnitude respectively. Flamsteedcatalogued 25 stars in the constellation, labelling them 1 to 25 Canum Venaticorum (CVn); however, 1CVn turned out to be in Ursa Major, 13CVn was in Coma Berenices, and 22CVn did not exist.[11]
Alpha Canum Venaticorum, also known as Cor Caroli ('heart of Charles'), is the constellation's brightest star, named by Sir Charles Scarborough in memory of King Charles I, the executed king of Britain.[12][c] The English astronomer William Henry Smyth wrote in 1844 that α CVn was brighter than usual during the Restoration, as Charles II returned to England to take the throne, but gave no source for this statement, which seems to be apocryphal.[14] Cor Caroli is a wide double star, with a primary of magnitude 2.9 and a secondary of magnitude 5.6; the primary is 110 light-years from Earth. The primary also has an unusually strong variable magnetic field.[12]
Beta Canum Venaticorum, or Chara, is a yellow-hued main sequence star of magnitude 4.25,[15] 27 light-years from Earth. Its common name comes from the word for joy.[12] It has been listed as an astrobiologically interesting star because of its proximity and similarity to the Sun.[16][17] However, no exoplanets have been discovered around it so far.[15]
AM Canum Venaticorum, a very blue star of magnitude 14, is the prototype of a special class of cataclysmic variable stars, in which the companion star is a white dwarf, rather than a main sequence star. It is 143 parsecs distant from the Sun.[19]
The Giant Void, an extremely large void (part of the universe containing very few galaxies), is within the vicinity of this constellation. It is regarded to be the second largest void ever discovered, slightly larger than the Eridanus Supervoid and smaller than the proposed KBC Void and 1,200 times the volume of expected typical voids. It was discovered in 1988 in a deep-sky survey. Its centre is approximately 1.5 billion light-years away.[22]
Deep-sky objects
Canes Venatici contains five Messier objects, including four galaxies. One of the more significant galaxies in Canes Venatici is the Whirlpool Galaxy (M51, NGC 5194) and NGC 5195, a small barred spiral galaxy that is seen face-on. This was the first galaxy recognised as having a spiral structure, this structure being first observed by Lord Rosse in 1845.[12] It is a face-on spiral galaxy 37 million light-years from Earth. Widely considered to be one of the most beautiful galaxies visible, M51 has many star-forming regions and nebulae in its arms, coloring them pink and blue in contrast to the older yellow core. M 51 has a smaller companion, NGC 5195, that has very few star-forming regions and thus appears yellow. It is passing behind M 51 and may be the cause of the larger galaxy's prodigious star formation.[23]
NGC 4707 is a spiral galaxy roughly 22 million light-years from Earth.[26]
Other notable spiral galaxies in Canes Venatici are the Sunflower Galaxy (M63, NGC 5055), M94 (NGC 4736), and M106 (NGC 4258).
M63, the Sunflower Galaxy, was named for its appearance in large amateur telescopes. It is a spiral galaxy with an integrated magnitude of 9.0.
M94 (NGC 4736) is a small face-on spiral galaxy with approximate magnitude 8.0, about 15 million light-years from Earth.[12]
NGC 4631 is a barred spiral galaxy, which is one of the largest and brightest edge-on galaxies in the sky.[27]
M3 (NGC 5272) is a globular cluster 32,000 light-years from Earth. It is 18′ in diameter, and at magnitude 6.3 is bright enough to be seen with binoculars. It can even be seen with the naked eye under particularly dark skies.[12]
M94, also cataloged as NGC 4736, is a face-on spiral galaxy 15 million light-years from Earth. It has very tight spiral arms and a bright core. The outskirts of the galaxy are incredibly luminous in the ultraviolet because of a ring of new stars surrounding the core 7,000 light-years in diameter. Though astronomers are not sure what has caused this ring of new stars, some hypothesize that it is from shock waves caused by a bar that is thus far invisible.[23]
^Hevelius' name for the northern dog, Asterion, is from the Greek αστέριον, meaning the 'little star',[6] the diminutive of αστηρ 'the star' or 'starry'. (Allen 1963, p. 115)
^Hevelius' name for the southern dog, Chara, is from the Greek χαρά, meaning 'joy'.(Allen 1963, p. 115)
^According to Warner,[13] it was originally named Cor Caroli Regis Martyris ('The Heart of King Charles the Martyr') for Charles I. Warner also notes that suggestions that the name was invented by Edmond Halley are erroneous.
^Kunitzsch, P.; Smart, T. (2006). A Dictionary of Modern Star Names: A short guide to 254 star names and their derivations (2nd revised ed.). Sky Publishing. p. 22. ISBN1-931559-44-9.
^Wagman, Morton (October 2003). Lost Stars: Lost, missing and troublesome stars from the catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and sundry others. Blacksburg, VA: McDonald and Woodward. p. 366. ISBN978-0-939923-78-6.
Kunitzsch, P. (1959). Arabische Sternnamen in Europa (in German). Otto Harassowitz.
Ptolemäus, Claudius (1974). Der Almagest: Die Syntaxis Mathematica des Claudius Ptolemäus in arabisch-lateinischer Ūberlieferung. Translated by Kunitzsch, P. Otto Harassowitz.
Ridpath, Ian; Tirion, Wil (2017), Guide to Stars and Planets (5th ed.), Princeton University Press, ISBN9780691177885
Kunitzsch, P. (1990). Der Sternkatalog des Almagest die arabisch-mittelalterliche Tradition (in German). Vol. II Die lateinische Ūbersetzung Gerhards von Cremona. Otto Harassowitz.
![NGC 4248 is located about 24 million light-years away.[24]](File:A_cosmic_atlas_NGC_4248.jpg)
![NGC 4242 is a dim galaxy in Canes Venatici.[25]](File:Dim_and_diffuse.jpg)
![NGC 4707 is a spiral galaxy roughly 22 million light-years from Earth.[26]](http://upload.wikimedia.org/wikipedia/commons/thumb/6/6a/NGC_4707_-_HST_-_Potw1651a.tif/lossy-page1-120px-NGC_4707_-_HST_-_Potw1651a.tif.jpg)
