Tau Leonis

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τ Leonis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Leo
Right ascension 11h 27m 56.23976s[1]
Declination +02° 51′ 22.5609″[1]
Apparent magnitude (V) 5.00[2]
Spectral type G8- IIIa[3]
U−B color index +0.80[2]
B−V color index +1.005[2]
Radial velocity (Rv) −8.90[4] km/s
Proper motion (μ) RA: +16.89[1] mas/yr
Dec.: −9.81[1] mas/yr
Parallax (π) 5.80 ± 0.33[1] mas
Distance 560 ± 30 ly
(172 ± 10 pc)
Mass 3.90±0.19[5] M
Radius 25.14±1.55[5] R
Luminosity 329.6±39.6[5] L
Surface gravity (log g) 2.25±0.05[5] cgs
Temperature 4,910±33[5] K
Metallicity [Fe/H] −0.07±0.10[5] dex
Age 190±20[5] Myr
Other designations
τ Leo, 84 Leo, BD+03° 2504, FK5 1297, HD 99648, HIP 55945, HR 4418, SAO 118875.[6]

Tau Leonis (τ Leo) is a star in the constellation Leo. It has an apparent visual magnitude of 5.00,[2] which is bright enough to be seen with the naked eye. The distance to this star, as estimated using parallax measurements,[1] is 560 light years.

This G-type giant star has a stellar classification of G8- IIIa[3] and currently resides on the red giant branch. It has about 390% of the Sun's mass. The star is much younger than the Sun, with an age of around 190 million years. As an evolved giant, it has expanded to about 25 times the Sun's radius and radiates 330 time the luminosity of the Sun. The effective temperature of the outer atmosphere is 4,910 K.[5]


  1. ^ a b c d e f van Leeuwen, F. (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 ^ a b c d Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373. 
  4. ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048free to read, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61. 
  5. ^ a b c d e f g h Hekker, S.; Meléndez, J. (2007), "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters", Astronomy and Astrophysics, 475 (3): 1003–1009, arXiv:0709.1145free to read, Bibcode:2007A&A...475.1003H, doi:10.1051/0004-6361:20078233. 
  6. ^ "tau Leo -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-09-29.