Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||12h 56m 01.66622s|
|Declination||+38° 19′ 06.1541″|
|Apparent magnitude (V)||2.84 to 2.98|
|Right ascension||12h 56m 00.43258s|
|Declination||+38° 18′ 53.3768″|
|Apparent magnitude (V)||5.60|
|U−B color index||-0.32|
|B−V color index||-0.12|
|Variable type||α2 CVn|
|U−B color index||-0.03|
|B−V color index||+0.34|
|Radial velocity (Rv)||-4.10 ± 0.2 km/s|
|Proper motion (μ)||RA: −235.08 mas/yr
Dec.: 53.54 mas/yr
|Parallax (π)||28.41 ± 0.90 mas|
|Distance||115 ± 4 ly
(35 ± 1 pc)
|Absolute magnitude (MV)||0.16 ± 0.08|
|Radial velocity (Rv)||-0.60 ± 0.9 km/s|
|Proper motion (μ)||RA: −232.86 mas/yr
Dec.: 55.69 mas/yr
|Parallax (π)||27.10 ± 9.54 mas|
|Distance||approx. 120 ly
(approx. 40 pc)
|Mass||2.97 ± 0.07 M☉|
|Radius||2.49 ± 0.26 R☉|
|Luminosity||101 ± 12 L☉|
|Surface gravity (log g)||3.9 ± 0.1 cgs|
|Temperature||11600 ± 500 K|
|Rotational velocity (v sin i)||18.4 ± 0.5 km/s|
|Mass||1.47 ± 0.15 M☉|
|Surface gravity (log g)||4.25 ± 0.22 cgs|
|Rotational velocity (v sin i)||18 km/s|
|α2 CVn: α CVn A, 12 CVn A, FK5 485, GC 17557, HD 112413, HIP 63125, HR 4915, SAO 63257.|
|α1 CVn: α CVn B, 12 CVn B, GC 17556, HD 112412, HIP 63121, HR 4914, SAO 63256.|
Cor Caroli is the traditional name for the binary star also designated Alpha Canum Venaticorum (α Canum Venaticorum, abbreviated Alpha CVn, α CVn), although the International Astronomical Union now regards the name as only applying to the brightest component. Alpha Canum Venaticorum is the brightest point of light in the northern constellation of Canes Venatici.
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 Edmund Halley and intended it to refer to Charles II. 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". 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.
In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 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, 67 Ursae Majoris. Consequently, Alpha Canum Venaticorum itself is known as 常陳一 (Cháng Chén yī, English: the First Star of Imperial Guards.) From this Chinese name, the name Chang Chen was derived.
Alpha Canum Venaticorum is a binary star with 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. The system lies approximately 110 light years from the Sun.
α2 Canum Venaticorum
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. 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. 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. 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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- "* alf01 CVn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 4 May 2017.
- "IAU Catalog of Star Names". Retrieved 28 July 2016.
- Cor Caroli, Stars, Jim Kaler. Accessed on line September 15, 2008.
- R.H. Allen, Star Names: Their Lore and Meaning.
- Robert Burnham, Jr. Burnham's Celestial Handbook, Volume 1, p. 359.
- Ian Ridpath: "Star Tales", Canes Venatici. See also Deborah J. Warner, The Sky Explored: Celestial Cartography 1500-1800.
- "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
- (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, ISBN 978-986-7332-25-7.
- (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.
- Richard Hinckley Allen: Star Names — Their Lore and Meaning: Canes Venatici
- "Cor Caroli", p. 49, The hundred greatest stars, James B. Kaler, Springer, 2002, ISBN 0-387-95436-8.