Cor Caroli

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Cor Caroli seen from northern England on March 1, 2011.

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.[1] Alpha CVn is the brightest point of light in the northern constellation of Canes Venatici.

Nomenclature[edit]

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.[2]

In the western world Alpha CVn 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.[3] 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".[4] 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.[5]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[6] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[7] 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.[8] Consequently, Alpha Canum Venaticorum itself is known as 常陳一 (Cháng Chén yī, English: the First Star of Imperial Guards.)[9] From this Chinese name, the name Chang Chen was derived.[10]

Stellar properties[edit]

Alpha CVn 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.

It marks the northern vertex of the asterism known as the Great Diamond or the Diamond of Virgo.

α² Canum Venaticorum[edit]

α² Canum Venaticorum
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canes Venatici
Right ascension 12h 56m 01.6674s[11]
Declination +38° 19′ 06.167″[11]
Apparent magnitude (V) 2.84 to 2.98[12]
Characteristics
Spectral type A0pSiEuHg[13]
U−B color index −0.32[13]
B−V color index −0.12[13]
V−R color index 0.0[11]
R−I color index −0.06[13]
Variable type ACV[12]
Astrometry
Radial velocity (Rv) −3.3 ± 2[11] km/s
Proper motion (μ) RA: −233.43[11] mas/yr
Dec.: 54.98[11] mas/yr
Parallax (π) 29.60 ± 1.04[11] mas
Distance 110 ± 4 ly
(34 ± 1 pc)
Absolute magnitude (MV) 0.3[14]
Details
Radius 4.10[15] R
Rotational velocity (v sin i) 29[13] km/s
Other designations
α Canum Venaticorum A, α CVn A, Alpha Canum Venaticorum A, Alpha CVn A, α2 CVn, Alpha2 Canum Venaticorum, Alpha2 CVn, 12 Canum Venaticorum A, 12 CVn A, ADS 8706 A, BD+39 2580A, CCDM J12560+3819A, FK5 485, GC 17557, HD 112413, HIP 63125, HR 4915, IDS 12514+3851 A, LTT 13717, NLTT 32338, PPM 76815, SAO 63257.[11][13]
Database references
SIMBAD data

α² Canum Venaticorum has spectral type A0, and has an apparent visual magnitude which varies between 2.84 and 2.98, with a period of 5.47 days.[11][12] 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.[16] 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.[2][16] This star is the prototype of a class of variable stars, the so-called α² Canum Venaticorum stars. 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[edit]

α1 Canum Venaticorum
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canes Venatici
Right ascension 12h 56m 00.4522s[17]
Declination +38° 18′ 53.685″[17]
Apparent magnitude (V) 5.60[17]
Characteristics
Spectral type F0V[17]
U−B color index −0.03[18]
B−V color index +0.34[18]
V−R color index 0.3[17]
R−I color index +0.23[18]
Astrometry
Radial velocity (Rv) −3.1 ± 2[17] km/s
Proper motion (μ) RA: −203.89[17] mas/yr
Dec.: 88.34[17] mas/yr
Parallax (π) 29.60 ± 1.04[19] mas
Distance 110 ± 4 ly
(34 ± 1 pc)
Absolute magnitude (MV) 4[14]
Details
Radius 1.29[20] R
Rotational velocity (v sin i) 8[18] km/s
Other designations
α1 CVn, Alpha1 Canum Venaticorum, Alpha1 CVn, α Canum Venaticorum B, α CVn B, Alpha Canum Venaticorum B, Alpha CVn B, 12 Canum Venaticorum B, 12 CVn B, ADS 8706 B, BD+39 2580B, BD+39 2580, CCDM J12560+3819B, GC 17556, HD 112412, HIP 63121, HR 4914, IDS 12514+3851 B, LTT 13718, NLTT 32336, PPM 76814, SAO 63256.[17][18]
Database references
SIMBAD data

α1 Canum Venaticorum is a F-type main sequence star. It is considerably fainter than its companion and has an apparent visual magnitude of approximately 5.60.[17]

Namesakes[edit]

USS Cor Caroli (AK-91) was a United States Navy Crater class cargo ship named after the star.

References[edit]

  1. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  2. ^ a b Cor Caroli, Stars, Jim Kaler. Accessed on line September 15, 2008.
  3. ^ R.H. Allen, Star Names: Their Lore and Meaning.
  4. ^ Robert Burnham, Jr. Burnham's Celestial Handbook, Volume 1, p. 359.
  5. ^ Ian Ridpath: "Star Tales", Canes Venatici. See also Deborah J. Warner, The Sky Explored: Celestial Cartography 1500-1800.
  6. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  7. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016. 
  8. ^ (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.
  9. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
  10. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Canes Venatici
  11. ^ a b c d e f g h i V* alf02 CVn -- Variable Star of alpha2 CVn type, database entry, SIMBAD. Accessed on line November 2, 2009.
  12. ^ a b c 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, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 2, 2009.
  13. ^ a b c d e f 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.
  14. ^ a b From apparent magnitude and parallax.
  15. ^ HD 112413, database entry, Catalog of Apparent Diameters and Absolute Radii of Stars (CADARS), 3rd edition, L. E. Pasinetti-Fracassini, L. Pastori, S. Covino, and A. Pozzi, CDS ID II/224. Accessed on line November 2, 2009.
  16. ^ a b "Cor Caroli", p. 49, The hundred greatest stars, James B. Kaler, Springer, 2002, ISBN 0-387-95436-8.
  17. ^ a b c d e f g h i j LTT 13718 -- High proper-motion Star, database entry, SIMBAD. Accessed on line November 2, 2009.
  18. ^ a b c d e HR 4914, 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.
  19. ^ NLTT 32336, database entry, New HIP-based parallaxes for 424 faint stars, A. Gould and J. Chanamé, CDS ID J/ApJS/150/455. Accessed on line November 2, 2009. Also see New Hipparcos-based Parallaxes for 424 Faint Stars, Andrew Gould and Julio Chanamé, The Astrophysical Journal Supplement Series 150, #2 (February 2004), pp. 455–464, doi:10.1086/381147, Bibcode2004ApJS..150..455G .
  20. ^ HD 112412, database entry, Catalog of Apparent Diameters and Absolute Radii of Stars (CADARS), 3rd edition, L. E. Pasinetti-Fracassini, L. Pastori, S. Covino, and A. Pozzi, CDS ID II/224. Accessed on line November 2, 2009.