Beta Herculis
Beta Herculis (β Herculis, abbreviated Beta Her, β Her), formally named Kornephoros /kɔːrˈnɛfərəs/, or Rutilicus, is a binary star and the brightest star in the northern constellation of Hercules at a base apparent visual magnitude of 2.81. This is a suspected variable star with an apparent magnitude that may rise as high as 2.76. Based upon parallax measurements, it is located at a distance of 139 light-years (43 parsecs) from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hercules |
| Right ascension | 16h 30m 13.19955s |
| Declination | +21° 29′ 22.6008″ |
| Apparent magnitude (V) | 2.81 |
| Characteristics | |
| Spectral type | G7 IIIa |
| U−B color index | +0.70 |
| B−V color index | +0.91 |
| R−I color index | +0.47 |
| Astrometry | |
| Radial velocity (Rv) | −25.5 km/s |
| Proper motion (μ) | RA: −99.15 mas/yr Dec.: −15.39 mas/yr |
| Parallax (π) | 23.44 ± 0.58 mas |
| Distance | 139 ± 3 ly (43 ± 1 pc) |
| Absolute magnitude (MV) | −0.49 ± 0.10 |
| Details | |
| A | |
| Mass | 2.9 M☉ |
| Radius | 17 R☉ |
| Luminosity | 151 L☉ |
| Surface gravity (log g) | 2.5 cgs |
| Temperature | 4,887 K |
| Metallicity [Fe/H] | –0.27 dex |
| Rotational velocity (v sin i) | 3.0 km/s |
| B | |
| Mass | 0.9 M☉ |
| Orbit | |
| Period (P) | 410.6 d |
| Semi-major axis (a) | 11.37 ± 0.51 mas |
| Eccentricity (e) | 0.55 |
| Inclination (i) | 53.8 ± 2.3° |
| Longitude of the node (Ω) | 341.9 ± 3.8° |
| Periastron epoch (T) | 15500.4 MJD |
| Argument of periastron (ω) (primary) | 24.6° |
| Other designations | |
| Database references | |
| SIMBAD | data |
Although Beta Herculis appears to the naked eye to be a single star, in July 1899 the American astronomer W. W. Campbell discovered from spectroscopic measurements that its radial velocity varies, and concluded that it has a companion.
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