Cor Caroli

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α Canum Venaticorum
The location of α Canum Venaticorum (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canes Venatici
α2 CVn
Right ascension 12h 56m 01.66622s[1]
Declination +38° 19′ 06.1541″[1]
Apparent magnitude (V) 2.84 to 2.98[2]
α1 CVn
Right ascension 12h 56m 00.43258s[1]
Declination +38° 18′ 53.3768″[1]
Apparent magnitude (V) 5.60[3]
Characteristics
α2 CVn
Spectral type A0pSiEuHg[4]
U−B color index −0.32[5]
B−V color index −0.12[5]
Variable type α2 CVn
α1 CVn
Spectral type F2V[6]
U−B color index −0.03[7]
B−V color index +0.34[7]
Astrometry
α2 CVn
Radial velocity (Rv)−4.1±0.2[8] km/s
Proper motion (μ) RA: −235.08[1] mas/yr
Dec.: 53.54[1] mas/yr
Parallax (π)32.7227±0.5844 mas[9]
Distance100 ± 2 ly
(30.6 ± 0.5 pc)
Absolute magnitude (MV)0.16±0.08[10]
α1 CVn
Radial velocity (Rv)−0.60 ± 0.9[11] km/s
Proper motion (μ) RA: −232.86[1] mas/yr
Dec.: 55.69[1] mas/yr
Parallax (π)30.6121±0.0666 mas[12]
Distance106.5 ± 0.2 ly
(32.67 ± 0.07 pc)
Details
α2 CVn
Mass2.97±0.07[10] M☉
Radius2.49±0.26[10] R☉
Luminosity101±12[10] L☉
Surface gravity (log g)3.9±0.1[10] cgs
Temperature11,600±500[10] K
Rotation5.46939 d[10]
Rotational velocity (v sin i)18.4±0.5[10] km/s
Age165+60
−70[10] Myr
α1 CVn
Mass1.47±0.15[13] M☉
Radius1.5[13] R☉
Surface gravity (log g)4.25±0.22[13] cgs
Temperature7,080[13] K
Rotational velocity (v sin i)18[14] km/s
Other designations
α CVn, Alpha CVn, 12 CVn, BD+39°2580, ADS 8706 AB, CCDM J12560+3819B[15]
α2 CVn: α CVn A, 12 CVn A, FK5 485, GC 17557, HD 112413, HIP 63125, HR 4915, SAO 63257[15]
α1 CVn: α CVn B, 12 CVn B, GC 17556, HD 112412, HIP 63121, HR 4914, SAO 63256[16]
Database references
SIMBADα2 CVn
α1 CVn

Cor Caroli /ˌkɔːr ˈkærəlaɪ/ is a binary star in the northern constellation of Canes Venatici. It is the brightest star in the constellation, lying at the third magnitude. The International Astronomical Union uses the name "Cor Caroli" specifically for the brighter star of the binary.[17] The system has the Bayer designation Alpha Canum Venaticorum or α Canum Venaticorum.

Nomenclature

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α Canum Venaticorum, Latinised to Alpha Canum Venaticorum, is the system's Bayer designation. The brighter of the two stars is designated α2 Canum Venaticorum, the fainter α1 Canum Venaticorum.[18]

In the western world Alpha Canum Venaticorum had no name until the 17th century, when it was named Cor Caroli, which means "Charles's Heart". There has been some uncertainty whether it was named in honour of King Charles I of England, who was executed in 1649 during the English Civil War, or of his son, Charles II, who restored the English monarchy to the throne in 1660. The name was coined in 1660 by Sir Charles Scarborough, physician to Charles II, who claimed the star seemed to shine exceptionally brightly on the night of Charles II's return to England. In Star Names, R.H. Allen claimed that Scarborough suggested the name to Edmond Halley and intended it to refer to Charles II.[19] However, Robert Burnham Jr. notes that "the attribution of the name to Halley appears in a report published by J. E. Bode at Berlin in 1801, but seems to have no other verification".[20] In Star Tales, Ian Ridpath points out that the name's first appearance on a star map was in the 1673 chart of Francis Lamb, who labelled it Cor Caroli Regis Martyris ('the heart of Charles the martyred king'), clearly indicating that it was seen as referring to Charles I.[21]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[22] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[23] included a table of the first two batches of names approved by the WGSN, which included Cor Caroli for the star α2 Canum Venaticorum.

In Chinese, 常陳 (Cháng Chén), meaning Imperial Guards, refers to an asterism consisting of α Canum Venaticorum, 10 Canum Venaticorum, Beta Canum Venaticorum, 6 Canum Venaticorum, 2 Canum Venaticorum and 67 Ursae Majoris.[24] Consequently, the Chinese name for Alpha Canum Venaticorum itself is 常陳一 (Cháng Chén yī, English: the First Star of Imperial Guards).[25] From this Chinese name, the name Chang Chen was derived.[26]

Stellar properties

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File:Cor Caroli 2011-03-01.jpeg
Cor Caroli seen from northern England on March 1, 2011

Alpha Canum Venaticorum is a binary pair of stars that marks the northern vertex of the asterism known as the Great Diamond or the Diamond of Virgo. The system lies approximately 110 light-years from the Sun.

The two stars are separated by an estimated 650 - 670 Astronomical Units, and orbit a common center of mass with a period around 8,000 years.[27] The pair have a combined apparent magnitude of 2.81. The two stars are 19.6 arcseconds apart in the sky and are easily resolved in small telescopes.

α2 Canum Venaticorum

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File:Alpha2CVnLightCurve.png
A light curve for α2 Canum Venaticorum, plotted from TESS data[28]

α2 Canum Venaticorum has a spectral type of A0, and has an apparent visual magnitude which varies between 2.84 and 2.98, with a period of 5.47 days.[2] It is a chemically peculiar star with a strong magnetic field, about 5,000 times as strong as the Earth's, and is also classified as an Ap/Bp star.[29] Its atmosphere has overabundances of some elements, such as silicon, mercury and europium. This is thought to be due to some elements sinking down into the star under the force of gravity while others are elevated by radiation pressure.[18][29] This star is the prototype of a class of variable stars, the so-called α2 Canum Venaticorum variables. The strong magnetic field of these stars is believed to produce starspots of enormous extent. Due to these starspots the brightness of α2 Canum Venaticorum stars varies considerably during their rotation.

α1 Canum Venaticorum

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α1 Canum Venaticorum is an F-type main-sequence star. It is considerably fainter than its companion and has an apparent visual magnitude of approximately 5.60.[3]

Namesakes

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Cor Caroli was a U.S. Navy Crater-class cargo ship named after the star.

References

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  1. ^ a b c d e f g h Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  2. ^ a b alf 2 CVn, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars Archived 2017-06-20 at the Wayback Machine, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 2, 2009.
  3. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  4. ^ HR 4915, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line November 2, 2009.
  5. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  6. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  7. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  8. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  9. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). (Erratum: Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).). Gaia EDR3 record for this source at VizieR.
  10. ^ a b c d e f g h i Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  11. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  12. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). (Erratum: Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).). Gaia EDR3 record for this source at VizieR.
  13. ^ a b c d Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  14. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  15. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  16. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  17. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  18. ^ a b Cor Caroli Archived 2008-07-04 at the Wayback Machine, Stars, Jim Kaler. Accessed on line September 15, 2008.
  19. ^ R.H. Allen, Star Names: Their Lore and Meaning.
  20. ^ Robert Burnham, Jr. Burnham's Celestial Handbook, Volume 1, p. 359.
  21. ^ Ian Ridpath: "Star Tales", Canes Venatici. See also Deborah J. Warner, The Sky Explored: Celestial Cartography 1500-1800.
  22. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  23. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  24. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value)..
  25. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived September 29, 2009, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  26. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Canes Venatici
  27. ^ Cor Caroli, The Heart of Charles, April 2019 Feature – University Television, Comcast 61/1095 & UVerse 99, University of Arkansas Little Rock, February 28, 2019. Retrieved 10 October 2025.
  28. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  29. ^ a b "Cor Caroli", p. 49, The hundred greatest stars, James B. Kaler, Springer, 2002, Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value)..

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