Theta Geminorum
Location of θ Geminorum (circled in red) | |
| 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] |
| Distance | 189 ± 2 ly (58.0 ± 0.6 pc) |
| Absolute magnitude (MV) | −0.18[5] |
| Details | |
| Mass | 1.80[6] M☉ |
| Radius | 5.1[7] R☉ |
| Luminosity | 93[8] L☉ |
| Surface gravity (log g) | 3.40±0.14[6] cgs |
| Temperature | 8,502±289[6] K |
| Rotational velocity (v sin i) | 133[9] km/s |
| Age | 252[6] Myr |
| Other designations | |
| θ Gem, The Gem,[10] 34 Gem, BD+34°1481, FK5 261, HD 50019, HIP 33018, HR 2540, SAO 59570.[11] | |
| Database references | |
| SIMBAD | data |
Theta Geminorum (θ Gem, θ Geminorum) is a single[12] 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.[13] 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.[14]
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.[15]
References
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