Phi Geminorum
Binary star system in the constellation Gemini
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Phi Geminorum, Latinized from φ Geminorum, is a binary star[7] in the constellation Gemini, to the southeast of Pollux. It is visible to the naked eye with an apparent visual magnitude of 4.95.[3] Based upon an annual parallax shift of 14.66 mas,[2] this system is located around 220 light years from the Sun.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Gemini[1] |
| Right ascension | 07h 53m 29.81390s[2] |
| Declination | +26° 45′ 56.8252″[2] |
| Apparent magnitude (V) | 4.95[3] |
| Characteristics | |
| Evolutionary stage | main sequence[4] |
| Spectral type | A3 V[5] |
| U−B color index | +0.08[3] |
| B−V color index | +0.10[3] |
| Astrometry | |
| Radial velocity (Rv) | +8.0[6] km/s |
| Proper motion (μ) | RA: −34.69[2] mas/yr Dec.: -30.10[2] mas/yr |
| Parallax (π) | 14.66±0.73 mas[2] |
| Distance | 220 ± 10 ly (68 ± 3 pc) |
| Absolute magnitude (MV) | +0.81[1] |
| Orbit | |
| Period (P) | 581.751 d[7] |
| Eccentricity (e) | 0.0[7] |
| Details | |
| Mass | 1.9[8] M☉ |
| Luminosity | 36.5[9] L☉ |
| Surface gravity (log g) | 4.0[8] cgs |
| Temperature | 8,551±291[8] K |
| Rotational velocity (v sin i) | 165[10] km/s |
| Age | 637[8] Myr |
| Other designations | |
| φ Gem, 83 Geminorum, BD+27°1499, FK5 1207, HD 64145, HIP 38538, HR 3067, SAO 79774.[11] | |
| Database references | |
| SIMBAD | data |
The two components of this system have a circular orbit with a period of 582 days.[7] The primary component is an A-type main sequence star with a stellar classification of A3 V.[5] It is around 600 million years old and spinning relatively rapidly with a projected rotational velocity of 165[10] 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.[5] The star has nearly double the mass of the Sun and radiates 36.5[9] times the solar luminosity from its outer atmosphere at an effective temperature of 8,551[8] K.