HD 72945
HD 72945 and HD 72946 form a co-moving star system in the northern constellation of Cancer. HD 72945 is a binary star that is dimly visible to the naked eye as a point of light with an apparent visual magnitude of 5.91. At an angular separation of 10.10″ (as of 2020) is the fainter companion star HD 72946 at magnitude 7.25. It is being orbited by a brown dwarf. The system as a whole is located at a distance of approximately 84 light years from the Sun based on parallax measurements.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cancer |
| HD 72945 | |
| Right ascension | 08h 35m 50.978s |
| Declination | 06° 37′ 12.77″ |
| Apparent magnitude (V) | 5.91 |
| HD 72946 | |
| Right ascension | 08h 35m 51.267s |
| Declination | 06° 37′ 21.95″ |
| Apparent magnitude (V) | 7.25 |
| Characteristics | |
| HD 72945 | |
| Evolutionary stage | Main sequence |
| Spectral type | F8 V |
| B−V color index | 0.530±0.007 |
| HD 72946 | |
| Spectral type | G5V |
| B−V color index | 0.710±0.015 |
| Astrometry | |
| HD 72945 | |
| Radial velocity (Rv) | 26.61±0.15 km/s |
| Proper motion (μ) | RA: −130.308 mas/yr Dec.: −133.119 mas/yr |
| Parallax (π) | 38.4212 ± 0.1515 mas |
| Distance | 84.9 ± 0.3 ly (26.0 ± 0.1 pc) |
| Absolute magnitude (MV) | 3.91 |
| HD 72946 | |
| Radial velocity (Rv) | 28.75±0.14 km/s |
| Proper motion (μ) | RA: −136.593 mas/yr Dec.: −137.148 mas/yr |
| Parallax (π) | 38.9809 ± 0.0412 mas |
| Distance | 83.67 ± 0.09 ly (25.65 ± 0.03 pc) |
| Absolute magnitude (MV) | 5.16 |
| Orbit | |
| Primary | HD 72945 A |
| Period (P) | 14.2995±0.0001 d |
| Semi-major axis (a) | ≥4.07 ± 0.05 Gm (5.850 ± 0.072 R☉) |
| Eccentricity (e) | 0.332±0.008 |
| Periastron epoch (T) | 2,446,781.30±0.12 JD |
| Argument of periastron (ω) (secondary) | 227.1±3.0° |
| Semi-amplitude (K1) (primary) | 21.95±0.15 km/s |
| Details | |
| HD 72945 | |
| Mass | 1.245±0.030 M☉ |
| Radius | 1.358 R☉ |
| Luminosity | 2.372 L☉ |
| Surface gravity (log g) | 4.32 cgs |
| Temperature | 6,222 K |
| Metallicity [Fe/H] | 0.05 dex |
| Rotational velocity (v sin i) | 7.1 km/s |
| Age | 1.584±0.952 Gyr |
| HD 72946 | |
| Mass | 1.02±0.04 M☉ |
| Radius | 0.97±0.02 R☉ |
| Luminosity | 0.84 L☉ |
| Surface gravity (log g) | 4.69 cgs |
| Temperature | 5,670 K |
| Metallicity [Fe/H] | 0.16 dex |
| Rotational velocity (v sin i) | 4.14 km/s |
| Age | 1.9+0.6 −0.5 Gyr |
| Other designations | |
| HD 72945: Boss 2285, GC 11781, HIP 42172, HR 3395, SAO 116929, PPM 154707, NLTT 19856 | |
| HD 72946: Boss 2286, GC 16412, HIP 42173, HR 3396, SAO 116931, PPM 154708, NLTT 19851 | |
| Database references | |
| SIMBAD | HD 72945 |
| HD 72946 | |
The discovery of this double star was announced by F. G. W. Struve in 1782, and later given the discovery code STF 1245. Their common proper motion was confirmed by A. van Maanen in 1916, and this suggested they are physically associated. The projected separation of the two systems is 258.9 AU. Based on astrometric measurements from the Gaia spacecraft, the semimajor axis of this system is 200+52
−41 AU. Assuming they are gravitationally bound, they would have an orbital period of around 2,500 years.
There is an additional candidate stellar companion at an angular separation of ~130″, which would make this a four star system. (This object has the 2MASS designation J08354678+0635294.) Three additional faint companions detected by Struve are most likely background stars.