Epsilon Cancri
Epsilon Cancri (ε Cancri, abbreviated Epsilon Cnc, ε Cnc) is a white-hued binary star system in the zodiac constellation of Cancer. It is the brightest member of the Beehive Cluster with an apparent visual magnitude of +6.29, which is near the lower limit of visibility with the naked eye. The annual parallax shift of 5.4 mas as seen from Earth yields a distance estimate of approximately 606 light-years from the Sun.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cancer |
| ε Cnc A | |
| Right ascension | 08h 40m 27.01010s |
| Declination | 19° 32′ 41.3243″ |
| Apparent magnitude (V) | 6.29 |
| HD 73711 | |
| Right ascension | 08h 40m 18.09670s |
| Declination | 19° 31′ 55.1636″ |
| Apparent magnitude (V) | 7.535 |
| Characteristics | |
| ε Cnc A | |
| Spectral type | A5 III (kA3hA5mF0) |
| U−B color index | +0.16 |
| B−V color index | +0.17 |
| HD 73711 | |
| Spectral type | F0III (kA3hA5mF0) |
| Astrometry | |
| ε Cnc A | |
| Radial velocity (Rv) | +29.9±1.1 km/s |
| Proper motion (μ) | RA: −36.293 mas/yr Dec.: −12.133 mas/yr |
| Parallax (π) | 5.3836 ± 0.0474 mas |
| Distance | 606 ± 5 ly (186 ± 2 pc) |
| Absolute magnitude (MV) | +0.00 |
| HD 73711 | |
| Proper motion (μ) | RA: −36.251 mas/yr Dec.: −12.118 mas/yr |
| Parallax (π) | 5.4103 ± 0.0308 mas |
| Distance | 603 ± 3 ly (185 ± 1 pc) |
| Orbit | |
| Primary | ε Cnc Aa |
| Companion | ε Cnc Ab |
| Period (P) | 35.14101±0.00005 d |
| Semi-major axis (a) | 1.9127±0.0004 mas |
| Eccentricity (e) | 0.4195±0.0003 |
| Inclination (i) | 81.454±0.010° |
| Longitude of the node (Ω) | 356.069±0.014° |
| Periastron epoch (T) | 2448314.598 ± 0.016 |
| Argument of periastron (ω) (primary) | 258.38±0.02° |
| Semi-amplitude (K1) (primary) | 56.60±0.03 km/s |
| Semi-amplitude (K2) (secondary) | 61.55±0.10 km/s |
| Details | |
| ε Cnc Aa | |
| Mass | 2.420 M☉ |
| Radius | 4.8 R☉ |
| Luminosity | 90 L☉ |
| Surface gravity (log g) | 3.49 cgs |
| Temperature | 8,163 K |
| Metallicity [Fe/H] | +0.10 dex |
| Rotational velocity (v sin i) | 49.2 km/s |
| Age | 637 ± 19 Myr |
| ε Cnc Ab | |
| Mass | 2.226 M☉ |
| HD 73711 | |
| Mass | 2.54 M☉ |
| Radius | 2.4 R☉ |
| Luminosity | 43.5 L☉ |
| Surface gravity (log g) | 4.09 cgs |
| Temperature | 9,572 K |
| Metallicity [Fe/H] | +0.79 dex |
| Rotational velocity (v sin i) | 56.3 km/s |
| Age | 407 Myr |
| Other designations | |
| ε Cancri: Meleph, ε Cnc, 41 Cancri, BD+20°2171, GC 11904, HD 73731, HIP 42556, HR 3429, SAO 98024, GSC 01395-02733 | |
| HD 73711: BD+20°2163, GC 11893, HD 73711, SAO 98018 | |
| Database references | |
| SIMBAD | ε Cancri |
| HD 73711 | |
The binary pair has the designation WDS J08405+1933. The primary star is designated Epsilon Cancri and the secondary is HD 73711. Epsilon Cancri is itself a spectroscopic binary with components designated Aa (also named Meleph) and Ab. HD 73711 is also suspected of being a spectroscopic binary.
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