Eta Capricorni
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Capricornus |
| Right ascension | 21h 04m 24.30132s |
| Declination | −19° 51′ 17.9711″ |
| Apparent magnitude (V) | +4.84 (5.02 + 7.39) |
| Characteristics | |
| Spectral type | A4 V + F2 V |
| U−B color index | +0.09 |
| B−V color index | +0.17 |
| Astrometry | |
| Proper motion (μ) | RA: −37.62±0.90 mas/yr Dec.: −24.95±0.88 mas/yr |
| Parallax (π) | 20.20±0.82 mas |
| Distance | 161 ± 7 ly (50 ± 2 pc) |
| Absolute magnitude (MV) | +1.35 |
| Orbit | |
| Period (P) | 27.85±0.15 yr |
| Semi-major axis (a) | 0.265±0.003″ |
| Eccentricity (e) | 0.410±0.005 |
| Inclination (i) | 162.6±0.5° |
| Longitude of the node (Ω) | 171.1±15.0° |
| Periastron epoch (T) | 2002.46±0.09 |
| Argument of periastron (ω) (secondary) | 238.2±15.0° |
| Details | |
| η Cap A | |
| Mass | 2.03±0.12 M☉ |
| Luminosity | 24 L☉ |
| Metallicity [Fe/H] | −0.01 dex |
| η Cap B | |
| Mass | 1.21±0.07 M☉ |
| Other designations | |
| η Cap, 22 Cap, BD−20°6115, HD 200499, HIP 104019, HR 8060, SAO 189986, WDS J21044-1951AB | |
| Database references | |
| SIMBAD | data |
Eta Capricorni, Latinized from η Capricorni, is a binary star system in the southern constellation of Capricornus. It can be seen with the naked eye, having a combined apparent visual magnitude of +4.84. Based upon an annual parallax shift of 20.20 mas as seen from the Earth, the star is located about 161 light years from the Sun.
The pair orbit each other with a period of 27.85 years, a semimajor axis of 0.265 arc seconds, an eccentricity of 0.410. The primary member, component A, is a white-hued A-type main sequence star with an apparent magnitude of +5.02. Its companion, component B, has an apparent magnitude of +7.39.