Theta Geminorum

θ Geminorum
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Gemini
Right ascension 06h 52m 47.33887s[1]
Declination +33° 57′ 40.5175″[1]
Apparent magnitude (V) 3.59[2]
Characteristics
Spectral type A2 IV[3]
U−B color index +0.13[2]
B−V color index +0.10[2]
Astrometry
Radial velocity (Rv)+21[4] km/s
Proper motion (μ) RA: −1.66[1] mas/yr
Dec.: −47.31[1] mas/yr
Parallax (π)17.25 ± 0.19 mas[1]
Distance189 ± 2 ly
(58.0 ± 0.6 pc)
Absolute magnitude (MV)−0.18[5]
Details
Mass1.80[6] M☉
Radius5.1[7] R☉
Luminosity93[8] L☉
Surface gravity (log g)3.40±0.14[6] cgs
Temperature8,502±289[6] K
Rotational velocity (v sin i)133[9] km/s
Age252[6] Myr
Other designations
θ Gem, 34 Gem, BD+34°1481, FK5 261, HD 50019, HIP 33018, HR 2540, SAO 59570.[10]
Database references
SIMBADdata

Theta Geminorum (θ Gem, θ Geminorum) is a single[11] star in the northern zodiac constellation of Gemini. It is visual to the naked eye with an apparent visual magnitude of 3.59.[2] Based upon an annual parallax shift of 17.25 mas,[1] it is about 189 light years distant from the Sun.

This is an evolving A-type subgiant star with a stellar classification of A2 IV.[3] It has 1.80[6] times the mass of the Sun and radiates 93[8] times the solar luminosity. The measured angular diameter is 0.82±0.03 mas.[12] At an estimated distance of this star, this yields a physical size of about 5.1 times the radius of the Sun.[7] It is around 252 million years old and has a projected rotational velocity of 133[9] km/s. This rotation rate is giving the star an oblate shape, with an equatorial bulge that is 11% larger than the polar radius.[13]

The Washington Visual Double Star Catalog lists five visual companions within 100″; the closest and brightest such companion is the magnitude 8.6 θ Geminorum E at an angular separation of 2.4″ along a position angle of 295°, as of 2010.[14]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Mermilliod1986 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference abt1995 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference rgcrv was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference huang2012 was invoked but never defined (see the help page).
  6. ^ a b c d e Cite error: The named reference David2015 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference lang2006 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Mcdonald2012 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Royer2012 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Richichi2005 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference vanBelle2012 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference WDSC2014 was invoked but never defined (see the help page).