Theta Leonis

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Theta Leonis
Diagram showing star positions and boundaries of the Leo constellation and its surroundings
Cercle rouge 100%.svg

Location of θ Leonis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Leo
Right ascension 11h 14m 14.40446s[1]
Declination +15° 25′ 46.4541″[1]
Apparent magnitude (V) +3.324[2]
Characteristics
Spectral type A2 V[3]
U−B color index +0.07[2]
B−V color index –0.02[2]
Astrometry
Radial velocity (Rv) +7.6[4] km/s
Proper motion (μ) RA: -60.31[1] mas/yr
Dec.: -79.10[1] mas/yr
Parallax (π) 19.76 ± 0.17[1] mas
Distance 165 ± 1 ly
(50.6 ± 0.4 pc)
Details
Mass 2.5[5] M
Luminosity 141[5] L
Surface gravity (log g) 3.65[6] cgs
Temperature 9,350[6] K
Metallicity [Fe/H] +0.05[6] dex
Rotational velocity (v sin i) 23[7] km/s
Age 550[6] Myr
Other designations
70 Leo, HR 4359, BD+16 2234, HD 97633, SAO 99512, FK5 423, HIP 54879.[8]

Theta Leonis (θ Leonis, abbreviated Theta Leo, θ Leo), also named Chertan,[9] is a star in the constellation of Leo. With an apparent visual magnitude of +3.324[2] it is visible to the naked eye and forms one of the brighter stars in the constellation. The distance from the Sun can be directly determined from parallax measurements, yielding a value of about 165 light-years (51 parsecs).[1]

This is a large star with 2.5 times the mass of the Sun.[5] The spectrum matches a stellar classification of A2 V,[3] making this a seemingly typical A-type main sequence star. However, the spectrum shows enhanced absorption lines of metals, marking this as a chemically peculiar Am star.[10] The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, appears around 12% higher than in the Sun.[6] It is radiating 141[5] times the luminosity of the Sun from its outer atmosphere at an effective temperature of 9,350 K,[6] literally giving it a white-hot glow.[11]

Theta Leonis is much younger than the Sun, with an estimated age of around 550 million years.[6] It has a moderately high rate of rotation, with a projected rotational velocity of 23 km s−1.[7] Measurements in the infrared band show an excess of emission from the star and its surroundings, suggesting the presence of a circumstellar disk of dust. The temperature of this emission indicates the disk has an orbital radius of 36 AU.[6]

Nomenclature[edit]

θ Leonis (Latinised to Theta Leonis) is the star's Bayer designation.

It bore the traditional names Chertan, Chort and Coxa.[12] Chertan is derived from the Arabic al-kharātān 'two small ribs', originally referring to Delta Leonis and Theta Leonis; Chort from Arabic al-kharāt or al-khurt 'small rib', and Coxa is Latin for 'hip'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[14] included a table of the first two batches of names approved by the WGSN; which included Chertan for this star.

In Chinese, 太微右垣 (Tài Wēi Yòu Yuán), meaning Right Wall of Supreme Palace Enclosure, refers to an asterism consisting of Theta Leonis, Beta Virginis, Sigma Leonis, Iota Leonis and Delta Leonis.[15] Consequently, Theta Leonis itself is known as 太微右垣四 (Tài Wēi Zuǒ Yuán sì, English: the Fourth Star of Right Wall of Supreme Palace Enclosure.),[16] representing 西次相 (Xīcìxiāng), meaning The Second Western Minister.[17] 西次相 (Xīcìxiāng), spelled Tsze Seang by R.H. Allen, means "the Second Minister of State" [18]

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:0708.1752free to read, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J 
  3. ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819 
  4. ^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W 
  5. ^ a b c d Wyatt, M. C.; et al. (July 2007), "Steady State Evolution of Debris Disks around A Stars", The Astrophysical Journal, 663 (1): 365–382, arXiv:astro-ph/0703608free to read, Bibcode:2007ApJ...663..365W, doi:10.1086/518404 
  6. ^ a b c d e f g h Smith, K. C.; Dworetsky, M. M. (1993), "Elemental Abundances in Normal Late B-Stars and Hgmn-Stars from Co-Added IUE Spectra - Part One - Iron Peak Elements", Astronomy and Astrophysics, 274 (2): 335, Bibcode:1993A&A...274..335S 
  7. ^ 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/0610785free to read, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224 
  8. ^ "tet Leo -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-02-11 
  9. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  10. ^ Netopil, M.; et al. (November 2008), "Chemically peculiar stars and their temperature calibration", Astronomy and Astrophysics, 491 (2): 545–554, arXiv:0809.5131free to read, Bibcode:2008A&A...491..545N, doi:10.1051/0004-6361:200810325 
  11. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16 
  12. ^ Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the Solar System, Dover Books on Astronomy, 2 (2nd ed.), Courier Dover Publications, p. 1067, ISBN 0-486-23568-8 
  13. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  14. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016. 
  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.
  17. ^ (Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name, Hong Kong Space Museum. Accessed on line November 23, 2010.
  18. ^ [1]