Mu Andromedae
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h 56m 45.209s |
| Declination | +38° 29′ 57.60″ |
| Apparent magnitude (V) | 3.87 |
| Characteristics | |
| Spectral type | A5 V |
| U−B color index | +0.15 |
| B−V color index | +0.12 |
| Variable type | RS CVn |
| Astrometry | |
| Radial velocity (Rv) | +7.6 km/s |
| Proper motion (μ) | RA: +151.021 mas/yr Dec.: +34.800 mas/yr |
| Parallax (π) | 26.7046±0.6467 mas |
| Distance | 122 ± 3 ly (37.4 ± 0.9 pc) |
| Absolute magnitude (MV) | +0.86 |
| Orbit | |
| Period (P) | 550.7±0.2 d |
| Semi-major axis (a) | 46.66±0.06 mas |
| Eccentricity (e) | 0.8405±0.0009 |
| Inclination (i) | 52.5±0.3° |
| Longitude of the node (Ω) | −17.6±0.2° |
| Periastron epoch (T) | 55765.45 ± 0.04 MJD |
| Argument of periastron (ω) (secondary) | 168.9±0.3° |
| Semi-amplitude (K1) (primary) | 11.1±0.5 km/s |
| Details | |
| Mass | 2.21±0.09 M☉ |
| Radius | 3.03±0.11 R☉ |
| Luminosity | 40±3 L☉ |
| Surface gravity (log g) | 3.99 cgs |
| Temperature | 8,320±150 K |
| Metallicity [Fe/H] | +0.03 dex |
| Rotational velocity (v sin i) | 75 km/s |
| Age | 724±21 Myr |
| Other designations | |
| μ Andromedae, μ And, Mu And, 37 Andromedae, BD+37°175, FK5 33, HD 5448, HIP 4436, HR 269, SAO 54281, PPM 65785 | |
| Database references | |
| SIMBAD | data |
Mu Andromedae is a binary star system in the northern constellation of Andromeda. Its Bayer designation is Latinized from μ Andromedae, and abbreviated Mu And or μ And, respectively. The system has an apparent visual magnitude of 3.87, making it readily visible to the naked eye. Based upon parallax measurements, it is located at a distance of approximately 122 light-years (37 parsecs) from Earth. In the constellation, the star is situated about halfway between the bright star Mirach to the southwest and the Andromeda Galaxy (M31) to the northeast.
The spectrum of this star matches a stellar classification of A5 V, indicating that it is an A-type main sequence star. It has 2.2 times the mass of the Sun and three times the Sun's radius. The star is radiating about 40 times the luminosity of the Sun from its outer envelope at an effective temperature of 8,320 K, giving it the characteristic white glow of an A-type star. It is estimated to be about 724 million years old, with a relatively high projected rotational velocity of 75 km/s.
In 2007, Mu Andromedae was found to be a tidally-locked close binary system with an unseen companion. The two stars orbit each other every 550.7 days. The tidal interactions have spun up the primary star, causing it to become magnetically active and host unusually strong starspots.