Gamma Andromedae
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 02h 03m 53.95229s |
| Declination | +42° 19′ 47.0223″ |
| Apparent magnitude (V) | 2.27 |
| Characteristics | |
| Evolutionary stage | Candidate post-AGB |
| Spectral type | K2+IIb |
| U−B color index | +1.58 |
| B−V color index | +1.37 |
| R−I color index | +0.68 |
| Astrometry | |
| Radial velocity (Rv) | −11.7±0.9 km/s |
| Proper motion (μ) | RA: +42.32 mas/yr Dec.: −49.30 mas/yr |
| Parallax (π) | 8.30±1.04 mas |
| Distance | approx. 390 ly (approx. 120 pc) |
| Absolute magnitude (MV) | −3.09 |
| Orbit | |
| Primary | γ1 Andromedae |
| Companion | γ2 Andromedae |
| Period (P) | 4,748 yr |
| Details | |
| Radius | 98.5 R☉ |
| Luminosity | 2,987±412 L☉ |
| Surface gravity (log g) | 1.03 cgs |
| Temperature | 4,248 K |
| Metallicity [Fe/H] | −0.06 dex |
| Rotational velocity (v sin i) | < 17 km/s |
| Other designations | |
| Almach, Almaach, Almak, Almaak, Alamak, γ1 And, γ And A, 57 And A, BD+41 395, FK5 73, GC 2477, HD 12533, HIP 9640, HR 603, SAO 37734, PPM 44721, ADS 1630 A, CCDM J02039+4220A, WDS 02039+4220A | |
| Database references | |
| SIMBAD | data |
Gamma Andromedae is a multiple star system in the northern constellation of Andromeda. It is the third-brightest star in the constellation, after Alpheratz and Mirach. Its identifier is a Bayer designation that is Latinized from γ Andromedae, and is abbreviated Gam1 And or γ1 And, respectively. The system has the proper name Almach, pronounced /ˈælmæk/. Based on parallax measurements, it is estimated to be about 390 light-years distant. The system is drifting closer to the Sun with a radial velocity of −11.7 km/s.