Eta Andromedae
Eta Andromedae (Eta And, η Andromedae, η And) is a spectroscopic binary star in the constellation of Andromeda. It consists of two G-type subgiant or giant stars orbiting each other with a period of 115.7 days and has an overall apparent visual magnitude of approximately 4.403.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h 57m 12.4000s |
| Declination | +23° 25′ 03.533″ |
| Apparent magnitude (V) | 4.403 |
| Characteristics | |
| Spectral type | G8III-IV + G8III-IV |
| U−B color index | +0.69 |
| B−V color index | +0.94 |
| R−I color index | +0.48 |
| Astrometry | |
| η And A | |
| Radial velocity (Rv) | −10.3 ± 0.9 km/s |
| Proper motion (μ) | RA: −43.72 mas/yr Dec.: −46.06 mas/yr |
| Parallax (π) | 13.44 ± 0.75 mas |
| Distance | 240 ± 10 ly (74 ± 4 pc) |
| Absolute magnitude (MV) | 0.52 ± 0.06 |
| η And B | |
| Absolute magnitude (MV) | 1.07 ± 0.07 |
| Orbit | |
| Period (P) | 115.72 ± 0.01 d |
| Semi-major axis (a) | 10.37 ± 0.03 mas |
| Eccentricity (e) | 0.006 ± 0.002 |
| Inclination (i) | 30.5 ± 0.4° |
| Longitude of the node (Ω) | 69.4 ± 0.5° |
| Periastron epoch (T) | 48013 ± 1 MJD |
| Argument of periastron (ω) (secondary) | 215 ± 4° |
| Details | |
| η And A | |
| Mass | 2.6 ± 0.35 M☉ |
| Luminosity (bolometric) | 65 ± 3 L☉ |
| Surface gravity (log g) | 2.8 cgs |
| Temperature | 4900 K |
| Age | 800 Million years |
| η And B | |
| Mass | 2.3 ± 0.31 M☉ |
| Luminosity (bolometric) | 39 ± 3 L☉ |
| Surface gravity (log g) | 3.0 cgs |
| Temperature | 4900 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
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