HD 123
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| HD 123A | |
| Right ascension | 00h 06m 15.81387s |
| Declination | +58° 26′ 12.1073″ |
| Apparent magnitude (V) | 6.42 |
| HD 123B | |
| Right ascension | 00h 06m 15.71057s |
| Declination | +58° 26′ 12.6457″ |
| Apparent magnitude (V) | 7.32 |
| Characteristics | |
| Spectral type | G3V + (G8V + early MV) |
| B−V color index | 0.70 (A), 0.97 (B) |
| Astrometry | |
| HD 123A | |
| Radial velocity (Rv) | −11.7 ± 2 km/s |
| Proper motion (μ) | RA: 237.578 mas/yr Dec.: 37.174 mas/yr |
| Parallax (π) | 48.1027±0.0398 mas |
| Distance | 67.80 ± 0.06 ly (20.79 ± 0.02 pc) |
| HD 123B | |
| Radial velocity (Rv) | −16.0 ± 5 km/s |
| Proper motion (μ) | RA: 237.578 mas/yr Dec.: 37.174 mas/yr |
| Parallax (π) | 47.0168 ± 0.1936 mas |
| Distance | 69.4 ± 0.3 ly (21.27 ± 0.09 pc) |
| Orbit | |
| Primary | HD 123A |
| Companion | HD 123B |
| Period (P) | 106.83 yr |
| Semi-major axis (a) | 1.455±0.004" (29.5±0.6 AU) |
| Orbit | |
| Primary | HD 123Ba |
| Companion | HD 123Bb |
| Period (P) | 47.685±0.003 d |
| Eccentricity (e) | 0.610±0.024 |
| Periastron epoch (T) | MJD 49891.00±0.22 |
| Argument of periastron (ω) (secondary) | 290±4° |
| Details | |
| HD 123A | |
| Mass | 0.98 M☉ |
| HD 123Ba | |
| Mass | ~0.86 M☉ |
| Radius | ~0.87 (assumed) R☉ |
| Rotational velocity (v sin i) | 4.7 km/s |
| HD 123Bb | |
| Mass | ~0.31 M☉ |
| Other designations | |
| V640 Cassiopeiae, AG+58°10, BD+57°2865, GC 88, GJ 4.1, GJ 9001, HD 123, HIP 518, HR 5, SAO 21085, PPM 25002, ADS 61 AB, CCDM J00063+5826AB, WDS J00063+5826AB, G 243-13, LTT 10022, NLTT 213, TIC 347304641, 2MASS J00061575+5826128, WISEA J000616.14+582613.3 | |
| HD 123A: TIC 604446831, TYC 3664-1986-1 | |
| HD 123B: TIC 604446820, TYC 3664-1986-2 | |
| Database references | |
| SIMBAD | HD 123 |
| HD 123A | |
| HD 123B | |
HD 123 is a hierarchical triple star system in the deep northern constellation of Cassiopeia. It consists of a visual binary between HD 123A and B, of which component B is itself a spectroscopic binary (Ba & Bb). Through the use of a telescope, the visual pair can be resolved, with a separation that varies between 0.5 and 1.6 arcseconds. With a combined apparent magnitude of 5.98, it is faintly visible to the naked eye under dark skies as a yellow-hued star. The system is located approximately 70 light-years (21 pc) distant according to Hipparcos parallax measurements, while the Gaia EDR3 parallaxes for the individual stars point towards slightly closer distances of 67.8 ly (20.8 pc) and 69.4 ly (21.3 pc), respectively. It is trending closer towards the Solar System at a heliocentric radial velocity of −13.79 km/s.