Gamma Corvi

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Gamma Corvi
Diagram showing star positions and boundaries of the Corvus constellation and its surroundings
Cercle rouge 100%.svg

Location of γ Corvi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Corvus
Right ascension 12h 15m 48.37081s[1]
Declination –17° 32′ 30.9496″[1]
Apparent magnitude (V) 2.585[2]
Characteristics
Spectral type B8 III[3]
U−B color index –0.344[2]
B−V color index –0.111[2]
Astrometry
Radial velocity (Rv) -4.2[4] km/s
Proper motion (μ) RA: –158.61[1] mas/yr
Dec.: +21.86[1] mas/yr
Parallax (π) 21.23 ± 0.20[1] mas
Distance 154 ± 1 ly
(47.1 ± 0.4 pc)
Details
γ Crv A
Mass 4.2+0.4
−0.3
[5] or 5.7 ± 0.3[6] M
Radius 4.8 ± 0.4[6] R
Luminosity 1,260[6] L
Surface gravity (log g) 3.72 ± 0.20[6] cgs
Temperature 15,900 ± 700[6] K
Rotational velocity (v sin i) 30[7] km/s
Age 160+40
−30
[5] Myr
γ Crv B
Mass 0.8[8] M
Other designations
BD–16 3424, FK5 457, HD 106625, HIP 59803, HR 4662, SAO 157176.[9]

Gamma Corvi (γ Crv, γ Corvi) is the brightest star in the southern constellation of Corvus, having an apparent visual magnitude of 2.6.[2] Its traditional name is Gienah, which it shares with Epsilon Cygni. The name "Gienah Corvi", or "Gienah Ghurab", may be used to distinguish it from this star in Cygnus. The distance to this star has been measured directly using the parallax technique, yielding an estimated 154 light-years (47 parsecs) from Earth.[1]

Properties[edit]

This is a giant star with a stellar classification of B8 III.[3] It has around five times the Sun's radius,[6] with mass estimates ranging from 4.2[5] to 5.7[6] times the mass of the Sun. Gamma Corvi is radiating 1,260[6] times the luminosity of the Sun from its outer atmosphere at an effective temperature of 15,900 K,[6] giving it a blue-white hue.[10] The spectrum of this star displays an anomalously higher than normal abundance of the elements mercury and manganese, making this an HgMn star.[11] However, there are other elements that show large over or under abundances.[12] This chemical peculiarity in an otherwise stable stellar atmosphere is most likely caused by separation of the elements through diffusion and gravitational settling.[11]

Gamma Corvi has a confirmed stellar companion with a mass of about 0.8 times the Sun's, which may be orbiting at a separation of around 50 AU over a 158 year period.[8][5] The photometry for this star suggests a stellar classification in the range K5–M5 V.[13]

Etymology and cultural significance[edit]

"Gienah" derives from Arabic, from Ulugh Beg's الجناح الغراب اليمن al-janāħ al-ghirāb al-yaman, meaning "the right wing of the crow", although on modern charts it marks the left wing. Al-janāħ al-ghirāb al-yaman or Djenah al Ghyrab al Eymen appeared in the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, which was translated into Latin as Dextra ala Corvi.[14]

In Chinese, 軫宿 (Zhěn Sù), meaning Chariot (asterism), refers to an asterism consisting of γ Corvi, ε Corvi, δ Corvi and β Corvi.[15] Consequently, γ Corvi itself is known as 軫宿一 (Zhěn Sù yī, English: the First Star of Chariot.).[16]

In astrology, Gienah is supposed to have a similar effect to Mars and Saturn, tending to promote greed and craftiness. It was one of the medieval Behenian stars, associated with onyx, burdock, and a crow-like kabbalistic symbol Agrippa1531 alaCorui.png. In this context it is sometimes referred to as Ala Corvi, "the wing of the crow or raven."[citation needed]

References[edit]

  1. ^ a b c d e f van Leeuwen, F. (November 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 
  2. ^ a b c d Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars 8: 59, Bibcode:1984SAAOC...8...59C 
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988MSS...C04....0H 
  4. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953QB901.W495..... 
  5. ^ a b c d Janson, Markus et al. (August 2011), "High-contrast Imaging Search for Planets and Brown Dwarfs around the Most Massive Stars in the Solar Neighborhood", The Astrophysical Journal 736 (2): 89, arXiv:1105.2577, Bibcode:2011ApJ...736...89J, doi:10.1088/0004-637X/736/2/89 
  6. ^ a b c d e f g h i Hubrig, S. et al. (January 2009), "New magnetic field measurements of beta Cephei stars and Slowly Pulsating B stars", Astronomische Nachrichten 330 (4): 317, arXiv:0902.1314, Bibcode:2009AN....330..317H, doi:10.1002/asna.200811187 
  7. ^ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590 
  8. ^ a b Roberts, Lewis C., "Adaptive Optics Photometry and Astrometry of Binary Stars. II. A Multiplicity Survey of B Stars", The Astronomical Journal 133 (2): 545, Bibcode:2007AJ....133..545R, doi:10.1086/510335 
  9. ^ "GIENAH CORVI -- Variable Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2010-05-02 
  10. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  11. ^ a b Adelman, S. J. et al. (February 2006), "Elemental abundance analyses with DAO spectrograms. XXIX. The mercury-manganese stars 53 Tau, β Tau, γ Crv, and υ Her", Astronomy and Astrophysics 447 (2): 685–690, Bibcode:2006A&A...447..685A, doi:10.1051/0004-6361:20053581 
  12. ^ Fremat, Y.; Houziaux, L. (April 1997), "Elemental abundances in the Hg-Mn star γ Corvi", Astronomy and Astrophysics 320: 580–585, Bibcode:1997A&A...320..580F 
  13. ^ Roberts, Lewis C., Jr.; Turner, Nils H.; ten Brummelaar, Theo A. (February 2007), "Adaptive Optics Photometry and Astrometry of Binary Stars. II. A Multiplicity Survey of B Stars", The Astronomical Journal 133 (2): 545–552, Bibcode:2007AJ....133..545R, doi:10.1086/510335 
  14. ^ Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket", Monthly Notices of the Royal Astronomical Society 55: 429, Bibcode:1895MNRAS..55..429K, doi:10.1093/mnras/55.8.429 
  15. ^ (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.
  16. ^ (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.

External links[edit]