Epsilon Hydrae
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 08h 46m 46.51223s |
| Declination | +06° 25′ 07.6855″ |
| Apparent magnitude (V) | AB: 3.38 C: 7.5 |
| Characteristics | |
| Spectral type | AB: G5 III + F0 V C: F5 |
| U−B color index | +0.37 |
| B−V color index | +0.68 |
| Astrometry | |
| Radial velocity (Rv) | 40.46±0.03 km/s |
| Proper motion (μ) | RA: −228.11 mas/yr Dec.: −43.82 mas/yr |
| Parallax (π) | 25.23±0.98 mas |
| Distance | 129 ± 5 ly (40 ± 2 pc) |
| Absolute magnitude (MV) | +0.39 |
| Orbit | |
| Primary | ε Hya A |
| Companion | ε Hya B |
| Period (P) | 15.074+0.013 −0.008 yr |
| Semi-major axis (a) | 0.252+0.001 −0.003″ |
| Eccentricity (e) | 0.654+0.004 −0.006 |
| Inclination (i) | 49.655+0.457 −0.817° |
| Longitude of the node (Ω) | 288.568+0.974 −0.712° |
| Periastron epoch (T) | 1900.812+0.055 −0.08 |
| Argument of periastron (ω) (secondary) | 51.525+8.921 −9.59° |
| Semi-amplitude (K1) (primary) | 8.05±0.14 km/s |
| Details | |
| ε Hya A | |
| Mass | 2.094+0.094 −0.129 M☉ |
| Radius | 7.92±1.27 R☉ |
| Luminosity | 44 L☉ |
| Surface gravity (log g) | 3.00±0.05 cgs |
| Temperature | 5,084±15 K |
| Metallicity [Fe/H] | −0.17±0.02 dex |
| Rotational velocity (v sin i) | 19 km/s |
| Age | 1.15+0.26 −0.22 Gyr |
| ε Hya B | |
| Mass | 1.661+0.188 −0.177 M☉ |
| Other designations | |
| Ashlesha, ε Hya, 11 Hydrae, BD+06 2036, HD 74874, HIP 43109, HR 3482, NSV 4244, SAO 117112 | |
| Database references | |
| SIMBAD | data |
Epsilon Hydrae (ε Hydrae, abbreviated Epsilon Hya, ε Hya) is a multiple star system of a combined third magnitude in the constellation of Hydra. Based upon parallax measurements obtained during the Hipparcos mission, it is located roughly 129 light-years (40 parsecs) distant from the Sun.
The system consists of a binary pair designated Epsilon Hydrae AB, whose two components are themselves designated Epsilon Hydrae A (formally named Ashlesha /ɑːʃˈleɪʃə/) and B, orbited by a spectroscopic binary designated Epsilon Hydrae C. A possible fourth component, designated Epsilon Hydrae D, shares a common proper motion with the other components and thus is most likely a gravitationally-bound member of the system.