39 Tauri

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This article is about A2 Tauri. For other stars with this Bayer designation, see A Tauri.
39 Tauri
Observation data
Epoch J2000      Equinox J2000
Constellation Taurus
Right ascension 04h 05m 20.25805s[1]
Declination +22° 00′ 32.0489″[1]
Apparent magnitude (V) 5.90[2]
Spectral type G5 V[3]
U−B color index +0.12[4]
B−V color index +0.62[4]
Radial velocity (Rv) +24.0 ± 0.1[5] km/s
Proper motion (μ) RA: +172.47[1] mas/yr
Dec.: –131.27[1] mas/yr
Parallax (π) 59.04 ± 0.33[1] mas
Distance 55.2 ± 0.3 ly
(16.94 ± 0.09 pc)
Mass 1.10 ± 0.10[2] M
Radius 0.96 ± 0.07[2] R
Luminosity 1.01[2] L
Surface gravity (log g) 4.52 ± 0.09[2] cgs
Temperature 5,903 ± 36[2] K
Metallicity [Fe/H] 0.14 ± 0.03[2] dex
Rotation 9.12[5] d
Rotational velocity (v sin i) 5.52[6] km/s
Age 1.0[2] Gyr
Other designations
39 Tau, BD+21 587, GJ 160 , HD 25680, HIP 19076, HR 1262, SAO 76438.[7]

39 Tauri is the Flamsteed designation for an unresolved binary star[8] in the northern constellation of Taurus. It has an apparent visual magnitude of 5.90,[7] so, according to the Bortle scale, it is faintly visible from suburban skies at night. Measurements made with the Hipparcos spacecraft show an annual parallax shift of 0.05904″,[1] which is equivalent to a distance of around 55.2 ly (16.9 pc) from the Sun.

A stellar classification of G5 V[3] matches that of a G-type main sequence star; the type of the secondary component is unknown. Stellar models indicate the primary component is similar in physical properties to the Sun, with 110% of the Sun's mass, 96% of the radius, and shining with almost the same luminosity.[2] The overall metallicity of the star—the abundance of elements other than hydrogen and helium—is similar to the Sun.[9] At a relatively youthful estimated age of one billion years,[2] it is rotating with a period of 9.12[5] days. Based upon Hipparcos data, it displays a mild variability with an amplitude of 0.06 magnitude.[10]

The space velocity components of 39 Tauri are: –25.0(U), –14.0(V), –6.0(W). The surface activity and kinematic properties of this star are consistent with membership in the IC 2391 moving group.[11] It is following an orbit through the Milky Way galaxy that has an eccentricity of 0.06 carrying it as close as 23.9 kly (7.34 kpc) to the Galactic Core, and as far away as 26.8 kly (8.21 kpc). The orbital inclination will carry the star no further than 33 ly (10 pc) away from the galactic plane.[9]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e f g h i j Ghezzi, L.; et al. (September 2010), "Stellar Parameters and Metallicities of Stars Hosting Jovian and Neptunian Mass Planets: A Possible Dependence of Planetary Mass on Metallicity", The Astrophysical Journal, 720 (2): 1290–1302, arXiv:1007.2681Freely accessible, Bibcode:2010ApJ...720.1290G, doi:10.1088/0004-637X/720/2/1290. 
  3. ^ a b Shenavrin, V. I.; et al. (January 2011), "Search for and study of hot circumstellar dust envelopes", Astronomy Reports, 55 (1): 31–81, Bibcode:2011ARep...55...31S, doi:10.1134/S1063772911010070. 
  4. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  5. ^ a b c López-Santiago, J.; et al. (May 2010), "A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age", Astronomy and Astrophysics, 515: A97, arXiv:1002.1663Freely accessible, Bibcode:2010A&A...514A..97L, doi:10.1051/0004-6361/200913437. 
  6. ^ Martínez-Arnáiz, R.; et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter", Astronomy and Astrophysics, 520: A79, arXiv:1002.4391Freely accessible, Bibcode:2010A&A...520A..79M, doi:10.1051/0004-6361/200913725. 
  7. ^ a b "39 Tau -- Variable Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2013-10-13. 
  8. ^ Roberts, Lewis C., Jr.; et al. (November 2005), "Adaptive Optics Photometry and Astrometry of Binary Stars", The Astronomical Journal, 130 (5): 2262–2271, Bibcode:2005AJ....130.2262R, doi:10.1086/491586. 
  9. ^ a b Casagrande, L.; et al. (June 2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy and Astrophysics, 530: A138, arXiv:1103.4651Freely accessible, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276. 
  10. ^ Adelman, S. J.; et al. (December 2000), "On the Variability of G0-G9 Stars", Information Bulletin on Variable Stars, 4993: 1, Bibcode:2000IBVS.4993....1A. 
  11. ^ Murgas, F.; et al. (April 2013), "Stellar activity as a tracer of moving groups", Astronomy and Astrophysics, 552: A27, arXiv:1302.6935Freely accessible, Bibcode:2013A&A...552A..27M, doi:10.1051/0004-6361/201219483. 

Coordinates: Sky map 04h 05m 20.26s, +22° 00′ 32.05″