| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cancer |
| Right ascension | 09h 12m 17.54871s[1] |
| Declination | +14° 59′ 45.7382″[1] |
| Apparent magnitude (V) | 6.77 |
| Characteristics | |
| Spectral type | G8V[2] + K1V[2] / L8[3][4] + ~L8[4] |
| B−V color index | 0.70 |
| Astrometry | |
| Radial velocity (Rv) | 49.8252±0.076[5] km/s |
| Proper motion (μ) | RA: −524.40±0.60[1] mas/yr Dec.: +245.64±0.29[1] mas/yr |
| Parallax (π) | 49.11 ± 0.54 mas[1] |
| Distance | 66.4 ± 0.7 ly (20.4 ± 0.2 pc) |
| Absolute magnitude (MV) | +4.95[6] |
| Orbit[5] | |
| Primary | 81 Cancri A |
| Companion | 81 Cancri B |
| Period (P) | 988.058 ± 0.34698 days |
| Semi-major axis (a) | 115.4 ± 0.63″ |
| Eccentricity (e) | 0.433256 ± 0.0034 |
| Inclination (i) | 124.1 ± 0.64° |
| Longitude of the node (Ω) | 317.6 ± 0.46° |
| Periastron epoch (T) | 1982.690 ± 0.0040 |
| Argument of periastron (ω) (secondary) | 170.731 ± 0.81° |
| Argument of periastron (ω) (primary) | 350.731 ± 0.81° |
| Semi-amplitude (K1) (primary) | 11.4908 ± 0.11 km/s |
| Semi-amplitude (K2) (secondary) | 12.1317 ± 0.14 km/s |
| Details | |
| 81 Cnc A | |
| Mass | 0.89±0.029[5] M☉ |
| Luminosity | 1.03[6] L☉ |
| Metallicity [Fe/H] | -0.14[7] dex |
| 81 Cnc B | |
| Mass | 0.85±0.026[5] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
81 Cancri (Pi1 Cancri, π1 Cancri) is a stellar system that lies approximately 66 light-years away. The main component of the system is a close binary, while a brown dwarf binary is located at a wide separation.
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