Phi Tauri


Phi Tauri
Taurus IAU.svg
Red circle.svg
Location of φ Tauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Taurus
Right ascension 04h 20m 21.21580s[1]
Declination +27° 21′ 02.7009″[1]
Apparent magnitude (V) +4.957[2]
Spectral type K1 III[2]
B−V color index 1.154[2]
Radial velocity (Rv)1.27[2] km/s
Proper motion (μ) RA: −28.90[1] mas/yr
Dec.: −78.28[1] mas/yr
Parallax (π)10.16 ± 0.26[1] mas
Distance321 ± 8 ly
(98 ± 3 pc)
Absolute magnitude (MV)−0.15[3]
Mass1.36±0.19 M
Radius19.04±0.56 R
Luminosity131.0±6.8 L
Surface gravity (log g)2.02±0.08 cgs
Temperature4,479±30 K
Metallicity [Fe/H]−0.32±0.10 dex
Rotational velocity (v sin i)1.0[5] km/s
Age4.74±2.56 Gyr
Other designations
φ Tau, 52 Tauri, BD+27° 655, HD 27382, HIP 20250, HR 1348, SAO 76558, ADS 3137, WDS J04204+2721A[6]
Database references

Phi Tauri (φ Tauri) is a solitary,[7] orange-hued star in the zodiac constellation of Taurus. It has an apparent visual magnitude of +4.96,[2] which indicates the star is faintly visible to the naked eye. Based upon an annual parallax shift of 10.16 mas as seen from Earth,[1] it is located roughly 321 light years distant from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.27 due to interstellar dust.[8]

This is an evolved, K-type giant star with a stellar classification of K1 III,[2] currently (97% probability) on the red giant branch. It has an estimated 1.36 times the mass of the Sun and has expanded to 19 times the Sun's radius. At the age of roughly five billion years, it is radiating 131 times the Sun's luminosity from its inflated photosphere at an effective temperature of 4,479 K.[4]

Phi Tauri has a magnitude 7.51 visual companion located at an angular separation of 48.80 arc seconds along a position angle of 258°, as of 2015. The pair form a yellow and blue double that is visible in small telescopes.[9] A fainter, magnitude 12.27 companion lies at a separation of 118.10 arc seconds along a position angle of 25°, as of 2001.[10]


  • With κ1, κ2, υ and χ, it composed the Arabic were the Arabs' Al Kalbain, the Two Dogs.[11] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Kalbain were the title for five stars : this star (φ) as Alkalbain I, χ as Alkalbain II, κ1 as Alkalbain III, κ2 as Alkalbain IV and υ as Alkalbain V.[12]
  • In Chinese, 礪石 (Lì Dàn), meaning Whetstone, refers to an asterism consisting of φ Tauri, ψ Tauri, 44 Tauri and χ Tauri. Consequently, the Chinese name for φ Tauri itself is 礪石四 (Lì Dàn sì, English: the Fourth Star of Whetstone.).[13]


  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:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  2. ^ a b c d e f Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114, 88.
  3. ^ Luck, R. Earle; Heiter, Ulrike (June 2007), "Giants in the Local Region", The Astronomical Journal, 133 (6): 2464–2486, Bibcode:2007AJ....133.2464L, doi:10.1086/513194.
  4. ^ a b Reffert, Sabine; et al. (2015), "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity", Astronomy & Astrophysics, 574: A116, arXiv:1412.4634, Bibcode:2015A&A...574A.116R, doi:10.1051/0004-6361/201322360, hdl:10722/215277, S2CID 59334290.
  5. ^ De Medeiros, J. R.; et al. (November 2000), "Rotation and lithium in single giant stars", Astronomy and Astrophysics, 363: 239–243, arXiv:astro-ph/0010273, Bibcode:2000A&A...363..239D.
  6. ^ "phi Tau". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-05.{{cite web}}: CS1 maint: postscript (link)
  7. ^ 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.
  8. ^ Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
  9. ^ Privett, Grant; Jones, Kevin (2013), The Constellation Observing Atlas, The Patrick Moore Practical Astronomy Series, Springer Science & Business Media, p. 187,, ISBN 978-1461476481.
  10. ^ Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22
  11. ^ Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 413
  12. ^ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology.
  13. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 22 日