66 Eridani
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 05h 06m 45.65314s |
| Declination | −04° 39′ 18.5939″ |
| Apparent magnitude (V) | 5.12 |
| Characteristics | |
| Spectral type | B9V |
| U−B color index | -0.16 |
| B−V color index | -0.06 |
| Variable type | α2 CVn? |
| Astrometry | |
| Radial velocity (Rv) | 32.28±0.10 km/s |
| Proper motion (μ) | RA: 10.70 mas/yr Dec.: −0.78 mas/yr |
| Parallax (π) | 10.56±0.34 mas |
| Distance | 309 ± 10 ly (95 ± 3 pc) |
| Absolute magnitude (MV) | 0.37 |
| Orbit | |
| Period (P) | 5.5226013 ± 0.0000020 d |
| Eccentricity (e) | 0.0844±0.0013 |
| Periastron epoch (T) | 2441356.499±0.017 |
| Argument of periastron (ω) (secondary) | 160.9±1.1° |
| Semi-amplitude (K1) (primary) | 102.83±0.20 km/s |
| Semi-amplitude (K2) (secondary) | 100.35±0.19 km/s |
| Details | |
| 66 Eri A | |
| Mass | 2.629±0.032 M☉ |
| Radius | 1.948±0.063 R☉ |
| Luminosity | 51.3±3.3 L☉ |
| Surface gravity (log g) | 4.28±0.03 cgs |
| Temperature | 11,077 K |
| Rotational velocity (v sin i) | 17.1±0.2 km/s |
| Age | 30 Myr |
| 66 Eri B | |
| Mass | 2.566±0.032 M☉ |
| Radius | 1.919±0.061 R☉ |
| Luminosity | 46.9±3.0 L☉ |
| Surface gravity (log g) | 4.28±0.03 cgs |
| Temperature | 10,914 K |
| Rotational velocity (v sin i) | 16.9±0.2 km/s |
| Other designations | |
| EN Eri, BD−04°1044, HD 32964, HIP 23794, HR 1657, SAO 131777 | |
| Database references | |
| SIMBAD | data |
66 Eridani is a binary star in the constellation of Eridanus. The combined apparent magnitude of the system is 5.12 on average. Parallax measurements by Hipparcos put the system at some 309 light-years (95 parsecs) away. It lies half a degree northwest of beta Eridani.
This is a spectroscopic binary: the two stars cannot be individually resolved, but periodic Doppler shifts in its spectrum mean there must be orbital motion. The two stars orbit each other every 5.5 days. Their orbit is fairly circular, with an eccentricity of 0.0844.
The combined spectrum of 66 Eridani matches that of a B-type main-sequence star, and the two stars have similar masses. The spectrum also shows excess of mercury and manganese, as it is a type of chemically peculiar star called a mercury-manganese star. 66 Eridani is an Alpha2 Canum Venaticorum variable. For this reason, it has been given the designation EN Eridani.