Pi Tauri

Pi Tauri

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Taurus
Right ascension	04^h 26^m 36.37093^s[1]
Declination	+14° 42′ 49.6126″[1]
Apparent magnitude (V)	+4.69[2]
Characteristics
Spectral type	G7 IIIa Fe-1[3]
U−B color index	+0.72[2]
B−V color index	+0.98[2]
Astrometry
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 mas[1]
Distance	420 ± 10 ly (128 ± 4 pc)
Absolute magnitude (MV)	−1.27[5]
Details
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
SIMBAD	data

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]

References

1. van Leeuwen, F. (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. Argue, A. N. (1966), "UBV photometry of 550 F, G and K type stars", Monthly Notices of the Royal Astronomical Society, 133 (4): 475–493, Bibcode:1966MNRAS.133..475A, doi:10.1093/mnras/133.4.475.
3. 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, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
5. 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, arXiv:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781.
6. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:

   ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(127.7\cdot 1.55\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 42.6\cdot R_{\bigodot }\end{aligned}}}$

7. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
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.