Phi Geminorum

From Wikipedia, the free encyclopedia
Jump to: navigation, search
φ Geminorum
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Gemini
Right ascension 07h 53m 29.81390s[1]
Declination +26° 45′ 56.8252″[1]
Apparent magnitude (V) 4.95[2]
Spectral type A3 V[3]
U−B color index +0.08[2]
B−V color index +0.10[2]
Radial velocity (Rv) +8.0[4] km/s
Proper motion (μ) RA: −34.69[1] mas/yr
Dec.: -30.10[1] mas/yr
Parallax (π) 14.66 ± 0.73[1] mas
Distance 220 ± 10 ly
(68 ± 3 pc)
Period (P) 581.751 d[5]
Eccentricity (e) 0.0[5]
Mass 1.9[6] M
Luminosity 36.5[7] L
Surface gravity (log g) 4.0[6] cgs
Temperature 8,551±291[6] K
Rotational velocity (v sin i) 165[8] km/s
Age 637[6] Myr
Other designations
φ Gem, 83 Geminorum, BD+27° 1499, FK5 1207, HD 64145, HIP 38538, HR 3067, SAO 79774.[9]
Database references

Phi Geminorum (φ Gem) is a binary star[5] in the constellation Gemini, to the southwest of Pollux. It is visible to the naked eye with an apparent visual magnitude of 4.95.[2] Based upon an annual parallax shift of 14.66 mas,[1] this system is located around 220 light years from the Sun.

The two components of this system have a circular orbit with a period of 582 days.[5] The primary component is an A-type main sequence star with a stellar classification of A3 V.[3] It is around 600 million years old and spinning relatively rapidly with a projected rotational velocity of 165[8] km/s. This rate of spin is giving the star an oblate shape with an equatorial bulge that is 6% larger than the polar radius.[3] The star has nearly double the mass of the Sun and radiates 36.5[7] times the solar luminosity from its outer atmosphere at an effective temperature of 8,551[6] K.


  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 ^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data, SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b c van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, Bibcode:2012A&ARv..20...51V, arXiv:1204.2572Freely accessible, doi:10.1007/s00159-012-0051-2. 
  4. ^ Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W. 
  5. ^ a b c d Abt, Helmut A. (August 2005), "Observed Orbital Eccentricities", The Astrophysical Journal, 629 (1): 507–511, Bibcode:2005ApJ...629..507A, doi:10.1086/431207. 
  6. ^ a b c d e David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, Bibcode:2015ApJ...804..146D, arXiv:1501.03154Freely accessible, doi:10.1088/0004-637X/804/2/146. 
  7. ^ a b 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. ^ a b Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, Bibcode:2007A&A...463..671R, arXiv:astro-ph/0610785Freely accessible, doi:10.1051/0004-6361:20065224. 
  9. ^ "phi Gem -- High proper-motion Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-12-08.