Wikipedia

Alpha Coronae Australis

Alpha Coronae Australis or α Coronae Australis, officially named Meridiana (/məˌrɪdiˈænə/),[10] is the brightest star in the constellation of Corona Australis and is located about 125 light-years from Earth.

α Coronae Australis
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 A2V[3]
U−B color index +0.06[4]
B−V color index +0.04[4]
Astrometry
Radial velocity (Rv)−18.40±1.78[5] km/s
Proper motion (μ) RA: 84.87[1] mas/yr
Dec.: −95.99[1] mas/yr
Parallax (π)26.02 ± 0.25 mas[1]
Distance125 ± 1 ly
(38.4 ± 0.4 pc)
Absolute magnitude (MV)1.11[6]
Details
Mass2.57[7] M☉
Radius2.21[3] R☉
Luminosity31[8] L☉
Surface gravity (log g)4.08[7] cgs
Temperature9,916±337[7] K
Rotational velocity (v sin i)195[9] km/s
Age254[2] Myr
Other designations
Meridiana, α CrA, Alf CrA, CD−38° 13350, FK5 718, GC 26360, HD 178253, HIP 94114, HR 7254, SAO 210990, IRAS 19060-3759, 2MASS J19092834-3754157[4]
Database references
SIMBADdata

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.[citation needed] The name Alphecca or Alphekka is Arabic, short for نير الفكّة nayyir al-fakka "the bright (star) of the broken (ring of stars)".[11] In 2016, the IAU organized a Working Group on Star Names (WGSN)[12] 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.[10]

In Chinese, 鱉 (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.[13] Consequently, the Chinese name for Alpha Coronae Australis itself is 鱉六 (Biēliù, English: the Sixth Star of River Turtle.).[14]

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.[8] It has an apparent magnitude of +4.10.[4] 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.[8] 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,[9] close to its breakup velocity.

See also edit

References edit

  1. ^ a b c d e 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. S2CID 18759600.
  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, S2CID 18154947
  3. ^ a b Cotten, Tara H.; Song, Inseok (July 2016). "A Comprehensive Census of Nearby Infrared Excess Stars". The Astrophysical Journal Supplement Series. 225 (1): 24. arXiv:1606.01134. Bibcode:2016ApJS..225...15C. doi:10.3847/0067-0049/225/1/15. S2CID 118438871. 15.
  4. ^ a b c d "* alf CrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-09-02.
  5. ^ Kharchenko, N. V.; et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
  6. ^ "α Coronae Australis (star)". Wolfram Alpha. Retrieved 2012-09-02.
  7. ^ a b c David, Trevor J.; Hillenbrand, Lynne A. (2015). "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. S2CID 33401607.
  8. ^ a b c Kaler, James B. "ALFECCA MERIDIANA (Alpha Coronae Australis)". Stars. University of Illinois. Retrieved 2012-09-02.
  9. ^ 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. S2CID 18475298.
  10. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  11. ^ 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.
  12. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  13. ^ (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.
  14. ^ (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.
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