Gamma Mensae
Astrometric binary star system in the constellation Mensa
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Gamma Mensae, Latinized from γ Mensae, is an orange-hued star system in the southern constellation of Mensa. The apparent visual magnitude of 5.19[2] indicates it is dimly visible to the naked eye. Based upon an annual parallax shift of 7.70 mas as seen from the Earth,[1] it is about 102 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.033 due to interstellar dust.[9] The system shows the high velocity kinematic properties of a population II star, but has Sun-like abundances of most elements.[11]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Mensa |
| Right ascension | 05h 31m 53.01393s[1] |
| Declination | −76° 20′ 27.4779″[1] |
| Apparent magnitude (V) | 5.19[2] |
| Characteristics | |
| Spectral type | K2 III[3][4] |
| U−B color index | +1.18[2] |
| B−V color index | +1.13[2] |
| Astrometry | |
| Radial velocity (Rv) | +56.7±0.8[5] km/s |
| Proper motion (μ) | RA: +140.646[6] mas/yr Dec.: +269.634[6] mas/yr |
| Parallax (π) | 31.1021±0.1519 mas[6] |
| Distance | 104.9 ± 0.5 ly (32.2 ± 0.2 pc) |
| Absolute magnitude (MV) | +2.70[7] |
| Orbit[8] | |
| Period (P) | 7.455±4.857 yr |
| Semi-major axis (a) | 51±10″ |
| Eccentricity (e) | 0.59±0.15 |
| Inclination (i) | 53±8° |
| Longitude of the node (Ω) | 117±90° |
| Periastron epoch (T) | 1995.111±4.085 |
| Argument of periastron (ω) (secondary) | 124±74° |
| Details[9] | |
| γ Men A | |
| Mass | 1.04 M☉ |
| Radius | 4.99 R☉ |
| Luminosity | 21 L☉ |
| Surface gravity (log g) | 2.76[3] cgs |
| Temperature | 4,491[3] K |
| Metallicity [Fe/H] | +0.22 dex |
| Age | 10.60 Gyr |
| Other designations | |
| γ Men, CD−76°222, HD 37763, HIP 25918, HR 1953, SAO 256201[10] | |
| Database references | |
| SIMBAD | data |
This is a probable astrometric binary system[4] with poorly constrained orbital elements. The visible member, component A, is an evolved K-type giant star with a stellar classification K2 III[3] At about 10.6 billion years of age, it has nearly the same mass as the Sun but has expanded to five times the Sun's radius.[9] The star shines with 21 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,491 K.[3]