Theta Leonis

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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]
Spectral type A2 V[3]
U−B color index +0.07[2]
B−V color index –0.02[2]
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)
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 Leo, θ Leonis) is a star in the constellation Leo. It has the traditional names Chertan, Chort and Coxa.[9] 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 Earth 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]


This star has the following traditional names:

  • Chertan (from Arabic al-kharātān = "two small ribs", originally referring to δ and θ Leonis)
  • Chort (from Arabic al-kharāt or al-khurt = "small rib")
  • Coxa (Latin for "hip")


  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 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/0703608, 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/0610785, 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. ^ 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 
  10. ^ Netopil, M. et al. (November 2008), "Chemically peculiar stars and their temperature calibration", Astronomy and Astrophysics 491 (2): 545–554, arXiv:0809.5131, 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