Cor Caroli

Cor Caroli /ˌkɔːr ˈkærəlaɪ/ is a binary star designated Alpha Canum Venaticorum or α Canum Venaticorum. The International Astronomical Union uses the name "Cor Caroli" specifically for the brighter star of the binary.[17] Alpha Canum Venaticorum is the brightest point of light in the northern constellation of Canes Venatici.

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

Nomenclature

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
Cor Caroli seen from northern England on March 1, 2011

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.

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

α2 Canum Venaticorum
A light curve for α2 Canum Venaticorum, plotted from TESS data[27]

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.[28] 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][28] 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

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

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

References
  1. van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. 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. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  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. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. (2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". The Astronomical Journal. 126 (4): 2048. arXiv:astro-ph/0308182. Bibcode:2003AJ....126.2048G. doi:10.1086/378365. S2CID 119417105.
  7. Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99. Bibcode:1966CoLPL...4...99J.
  8. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  9. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  10. Kochukhov, O.; Wade, G. A. (2010). "Magnetic Doppler imaging of α2 Canum Venaticorum in all four Stokes parameters". Astronomy and Astrophysics. 513: A13. arXiv:1002.0025. Bibcode:2010A&A...513A..13K. doi:10.1051/0004-6361/200913860. S2CID 53998003.
  11. Holmberg, J.; Nordström, B.; Andersen, J. (2007). "The Geneva-Copenhagen survey of the Solar neighbourhood II". Astronomy and Astrophysics. 475 (2): 519. arXiv:0707.1891. Bibcode:2007A&A...475..519H. doi:10.1051/0004-6361:20077221. S2CID 119054949.
  12. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  13. Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A.
  14. Royer, F.; Zorec, J.; Gómez, A. E. (2007). "Rotational velocities of A-type stars". Astronomy and Astrophysics. 463 (2): 671. arXiv:astro-ph/0610785. Bibcode:2007A&A...463..671R. doi:10.1051/0004-6361:20065224. S2CID 18475298.
  15. "* alf02 CVn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 4 May 2017.
  16. "* alf01 CVn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 4 May 2017.
  17. "IAU Catalog of Star Names". Retrieved 28 July 2016.
  18. 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. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  23. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  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, ISBN 978-986-7332-25-7.
  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. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  28. "Cor Caroli", p. 49, The hundred greatest stars, James B. Kaler, Springer, 2002, ISBN 0-387-95436-8.
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