HD 2942
HD 2942 is a triple star system in the constellation Andromeda located approximately 170 parsecs (550 ly) away.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h 32m 49.0863s |
| Declination | +28° 16′ 48.8676″ |
| Apparent magnitude (V) | 6.33 |
| Characteristics | |
| Spectral type | K0III+G6V+G8V |
| U−B color index | 0.80 |
| B−V color index | 0.99 |
| Astrometry | |
| Radial velocity (Rv) | −10.50±0.14 km/s |
| Proper motion (μ) | RA: −5.695±0.072 mas/yr Dec.: 6.101±0.039 mas/yr |
| Parallax (π) | 5.8690 ± 0.0434 mas |
| Distance | 556 ± 4 ly (170 ± 1 pc) |
| Orbit | |
| Primary | HD 2942Ba |
| Companion | HD 2942Bb |
| Period (P) | 7.4887 days |
| Eccentricity (e) | 0.055 |
| Periastron epoch (T) | HJD 2,451,060.5586 |
| Argument of periastron (ω) (secondary) | 293.40° |
| Semi-amplitude (K1) (primary) | 64.01 km/s |
| Semi-amplitude (K2) (secondary) | 66.34 km/s |
| Details | |
| HD 2942A | |
| Mass | 3.17 M☉ |
| HD 2942B | |
| Mass | 0.89 (Ba) 0.85 (Bb) M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Database references | |
| SIMBAD | data |
The primary component, a red giant of spectral type K0III, has an apparent magnitude of 6.33, meaning that it is barely visible with the naked eye under good conditions.
The secondary component is much fainter, with an apparent magnitude 11.26, and is located 8.6 arcseconds away. It is a double-lined spectroscopic binary, where two very similar G-type main sequence stars of spectral types G6V and G8V orbit around their common center of mass in 7.489 days. The pair complete an orbit around the primary star every 24,762 years.
Catalogues of stellar multiplicity, like the Washington Double Star Catalog, usually list another component; this star, however, is located much more far away than the other two.