Pi Tauri

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Pi Tauri
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Taurus
Right ascension 04h 26m 36.37093s[1]
Declination +14° 42′ 49.6126″[1]
Apparent magnitude (V) +4.69[2]
Spectral type G7 IIIa Fe-1[3]
U−B color index +0.72[2]
B−V color index +0.98[2]
Radial velocity (Rv) +31.4±0.3[4] km/s
Proper motion (μ) RA: −9.52[1] mas/yr
Dec.: −31.44[1] mas/yr
Parallax (π) 7.83 ± 0.22[1] mas
Distance 420 ± 10 ly
(128 ± 4 pc)
Absolute magnitude (MV) −1.27[5]
Mass 3.94[5] M
Radius 21[6] R
Luminosity 229[7] L
Surface gravity (log g) 2.54[5] cgs
Temperature 5,086[7] K
Metallicity [Fe/H] −0.08[5] dex
Age 17[5] Myr
Other designations
π Tau, 73 Tau, BD+14° 697, HD 28100, HIP 20732, HR 1396, SAO 93935[8]
Database references

Pi Tauri (π Tauri) is a solitary,[9] yellow-hued star in the zodiac constellation of Taurus. With an apparent visual magnitude of +4.69,[2] it is bright enough to be visible to the naked eye. Although it appears to lie among the stars of the Hyades cluster, it is not itself a member, being three times farther from Earth than the cluster. The distance to this star, as determined using an annual parallax shift of 7.83 mas as seen from the Earth,[1] is around 420 light years. At that range, the visual magnitude of the star is diminished by an extinction factor of 0.24 due to interstellar dust.[5]

This is an evolved G-type giant star with a stellar classification of G7 IIIa Fe-1,[3] where the suffix notation indicates an underabundance of iron in the spectrum. The measured angular diameter is 1.55±0.06 mas.[10] At the estimated distance of Pi Tauri, this yields a physical size of about 21 times the radius of the Sun.[6] It possesses nearly four[5] times the mass of the Sun and is radiating 229 times the Sun's luminosity at an effective temperature of 5,086 K.[7]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Argue, A. N. (1966), "UBV photometry of 550 F, G and K type stars", Monthly Notices of the Royal Astronomical Society, 133: 475–493, Bibcode:1966MNRAS.133..475A, doi:10.1093/mnras/133.4.475. 
  3. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, 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, Bibcode:2012A&A...546A..61D, arXiv:1208.3048Freely accessible, doi:10.1051/0004-6361/201219219, A61. 
  5. ^ a b c d e f g Takeda, Yoichi; et al. (August 2008), "Stellar Parameters and Elemental Abundances of Late-G Giants", Publications of the Astronomical Society of Japan, 60 (4): 781–802, Bibcode:2008PASJ...60..781T, arXiv:0805.2434Freely accessible, doi:10.1093/pasj/60.4.781. 
  6. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1.  The radius (R*) is given by:
  7. ^ a b c McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, Bibcode:2012MNRAS.427..343M, arXiv:1208.2037Freely accessible, doi:10.1111/j.1365-2966.2012.21873.x. 
  8. ^ "pi Tau". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-30. 
  9. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, Bibcode:2008MNRAS.389..869E, arXiv:0806.2878Freely accessible, doi:10.1111/j.1365-2966.2008.13596.x. 
  10. ^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.