Gamma Tauri

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γ Tauri
Taurus constellation map.svg
Red circle.svg

Location of γ Tauri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Taurus
Right ascension 04h 19m 47.6037s[1]
Declination +15° 37′ 39.512″[1]
Apparent magnitude (V) 3.654[2]
Spectral type G8III[3]
U−B color index +0.84[4]
B−V color index +0.99[4]
Radial velocity (Rv) 38.7 ± 0.9[5] km/s
Proper motion (μ) RA: +115.29[1] mas/yr
Dec.: -23.86[1] mas/yr
Parallax (π) 21.17 ± 1.17[1] mas
Distance 154 ± 9 ly
(47 ± 3 pc)
Absolute magnitude (MV) 0.22[3]
Mass 2.70 ± 0.13[6] M
Radius 13.4 ± 0.2[7] R
Luminosity 85[3] L
Surface gravity (log g) 2.58-2.61[7] cgs
Temperature 4,844 ± 47[7] K
Metallicity [Fe/H] +0.11[8] dex
Rotation 253 days[9]
Rotational velocity (v sin i) 4[10] km/s
Age 430–530[3][6] Myr
Other designations
Hyadum I, Prima Hyadum,[11] 54 Tauri, BD+15°612, FK5 159, HD 27371, HIP 20205, HR 1346, SAO 93868, GC 5226, CCDM 04198+1538.[2]
Database references

Gamma Tauri (γ Tau, γ Tauri) is a star in the constellation Taurus and a member of the Hyades star cluster. It has the traditional name Hyadum I,[11] which is Latin for "First Hyad".

Gamma Tauri is a spectral class G8 or K0[2][3] giant star with an apparent magnitude of +3.65. It is located within about 2.5 parsecs of the center of the Hyades cluster—the nearest open cluster to the Sun. This star has passed through the main sequence phase is now a red clump giant, meaning it is using nuclear fusion of helium at its core to provide energy.[12] Age estimates for Gamma Tauri range from 430 million[3] to 530 million years.[6] By comparison, the age of the Hyades cluster is about 625 million years with an error margin of 50 million years.[13]

Based upon parallax measurements, Gamma Tauri is approximately 154 light years from Earth. The angular diameter of this star has been measured using the CHARA array to 2% accuracy. After correcting for limb darkening, this gives the stellar radius as 13.4 times the radius of the Sun.[7] The star is radiating about 85 times the luminosity of the Sun[3] and has 2.7 times the Sun's mass.[6] With its large size and low projected rotational velocity of 4 km s−1,[10] it takes about 253 days to complete a rotation.[9]


  1. ^ a b c d e Perryman, M. A. C.; et al. (1997), "The Hipparcos Catalogue", Astronomy & Astrophysics, 323: L49–L52, Bibcode:1997A&A...323L..49P 
  2. ^ a b c "NSV 1553 - Variable Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2009-09-22. 
  3. ^ a b c d e f g Takeda, Yoichi; Sato, Bun'ei; Murata, Daisuke (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. 
  4. ^ a b Johnson, H. L.; Morgan, W. W. (1953). "Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas". Astrophysical Journal. 117: 313–352. Bibcode:1953ApJ...117..313J. doi:10.1086/145697. 
  5. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Retrieved 2009-09-10. 
  6. ^ a b c d da Silva, L.; et al. (November 2006). "Basic physical parameters of a selected sample of evolved stars". Astronomy and Astrophysics. 458 (2): 609–623. Bibcode:2006A&A...458..609D. arXiv:astro-ph/0608160Freely accessible. doi:10.1051/0004-6361:20065105. 
  7. ^ a b c d Boyajian, Tabetha S.; et al. (February 2009). "Angular Diameters of the Hyades Giants Measured with the CHARA Array". The Astrophysical Journal. 691 (2): 1243–1247. Bibcode:2009ApJ...691.1243B. arXiv:0810.2238Freely accessible. doi:10.1088/0004-637X/691/2/1243. 
  8. ^ Soubiran, C.; Bienaymé, O.; Mishenina, T. V.; Kovtyukh, V. V. (March 2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics. 480 (1): 91–101. Bibcode:2008A&A...480...91S. arXiv:0712.1370Freely accessible. doi:10.1051/0004-6361:20078788. 
  9. ^ a b Setiawan, J.; et al. (July 2004), "Precise radial velocity measurements of G and K giants. Multiple systems and variability trend along the Red Giant Branch", Astronomy and Astrophysics, 421: 241–254, Bibcode:2004A&A...421..241S, doi:10.1051/0004-6361:20041042-1 
  10. ^ a b Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239 (1). Bibcode:1970CoAsi.239....1B. 
  11. ^ a b Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 390. ISBN 0-486-21079-0. 
  12. ^ de Bruijne, J. H. J.; Hoogerwerf, R.; de Zeeuw, P. T. (February 2001). "A Hipparcos study of the Hyades open cluster. Improved colour-absolute magnitude and Hertzsprung-Russell diagrams". Astronomy and Astrophysics. 367 (1): 111–147. Bibcode:2001A&A...367..111D. arXiv:astro-ph/0011565Freely accessible. doi:10.1051/0004-6361:20000410. 
  13. ^ da Silva, L.; et al. (November 2006). "Basic physical parameters of a selected sample of evolved stars". Astronomy and Astrophysics. 458 (2): 609–623. Bibcode:2006A&A...458..609D. arXiv:astro-ph/0608160Freely accessible. doi:10.1051/0004-6361:20065105.