Alpha Coronae Australis

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α Coronae Australis
Diagram showing star positions and boundaries of the Corona Australis constellation and its surroundings
Cercle rouge 100%.svg
Location of α CrA (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Corona Australis
Right ascension  19h 09m 28.34097s[1]
Declination –37° 54′ 16.1022″[1]
Apparent magnitude (V) 4.102[2]
Characteristics
Spectral type A2Va[3]
U−B color index +0.06[3]
B−V color index +0.04[3]
Astrometry
Radial velocity (Rv)−18.4[3] km/s
Proper motion (μ) RA: 84.87[3] mas/yr
Dec.: −95.99[3] mas/yr
Parallax (π)26.02 ± 0.25[1] mas
Distance125 ± 1 ly
(38.4 ± 0.4 pc)
Absolute magnitude (MV)1.11[4]
Details
Mass2.3[5] M
Radius2.3[5] R
Luminosity31[5] L
Temperature9,100[5] K
Rotational velocity (v sin i)195[6] km/s
Age254[2] Myr
Other designations
Meridiana, α CrA, CD−38° 13350, HR 7254, HD 178253, FK5 718, HIP 94114, SAO 210990, GC 26360, IRAS 19060-3759, 2MASS J19092834-3754157
Database references
SIMBADdata

Alpha Coronae Australis (α Coronae Australis, abbreviated Alf CrA, α CrA), officially named Meridiana /məˌrɪdiˈænə/,[7] is the brightest star in the constellation of Corona Australis and is located about 125 light-years from Earth.

Nomenclature[edit]

α Coronae Australis (Latinised to Alpha Coronae Australis) is the star's Bayer designation.

It is the only star in the constellation with a traditional proper name, Alphekka Meridiana (Latin for 'Alphekka South'), after Alphecca, the brightest star in the constellation Corona Borealis; the name Alphecca or Alphekka is Arabic, short for نير الفكّة nayyir al-fakka "the bright (star) of the broken (ring of stars)".[8] In 2016, the IAU organized a Working Group on Star Names (WGSN)[9] to catalog and standardize proper names for stars; the WGSN approved the name Meridiana for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[7]

In Chinese, (Biē), meaning River Turtle, refers to an asterism consisting of Alpha Coronae Australis, Alpha Telescopii, Eta¹ Coronae Australis, Zeta Coronae Australis, Delta Coronae Australis, Beta Coronae Australis, Gamma Coronae Australis, Epsilon Coronae Australis, HD 175362, Kappa² Coronae Australis and Theta Coronae Australis.[10] Consequently, the Chinese name for Alpha Coronae Australis itself is 鱉六 (Biēliù, English: the Sixth Star of River Turtle.).[11]

Properties[edit]

Alpha Coronae Australis belongs to the spectral class A2Va, making it an A-type star like Vega. Like the latter, it has excess infrared radiation, which indicates it may be ringed by a disk of dust,[5] it has an apparent magnitude of +4.10.[3] The star's mass and radius are estimated at 2.3 times the Sun's mass and radius. With an effective temperature of roughly 9,100 K, the star radiates a total luminosity of about 31 times the Sun's;[5] this star is roughly 254 million years old.[2] A rapidly rotating star, it spins at almost 200 km per second at the equator, making a complete revolution in approximately 14 hours,[6] close to its breakup velocity.

See also[edit]

References[edit]

  1. ^ a b c 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 Song, Inseok; et al. (February 2001), "Ages of A-Type Vega-like Stars from uvbyβ Photometry", The Astrophysical Journal, 546 (1): 352–357, arXiv:astro-ph/0010102, Bibcode:2001ApJ...546..352S, doi:10.1086/318269
  3. ^ a b c d e f g "* alf CrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-09-02.
  4. ^ "α Coronae Australis (star)". Wolfram Alpha. Retrieved 2012-09-02.
  5. ^ a b c d e f Kaler, James B. "ALFECCA MERIDIANA (Alpha Coronae Australis)". Stars. University of Illinois. Retrieved 2012-09-02.
  6. ^ a b Royer, F.; Zorec, J.; Gómez, A. E. (February 2007). "Rotational velocities of A-type stars. III. Velocity distributions". Astronomy and Astrophysics. 463 (2): 671–682. arXiv:astro-ph/0610785. Bibcode:2007A&A...463..671R. doi:10.1051/0004-6361:20065224.
  7. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  8. ^ Allen, Richard Hinckley (1963) [1899]. Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. pp. 172–73. ISBN 0-486-21079-0.
  9. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  10. ^ (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.
  11. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.