Alpha Ophiuchi
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 34m 56.06945s |
| Declination | +12° 33′ 36.1346″ |
| Apparent magnitude (V) | 2.07 |
| Characteristics | |
| Spectral type | A5IVnn / K5–7 V |
| U−B color index | +0.10 |
| B−V color index | +0.15 |
| Astrometry | |
| Radial velocity (Rv) | +12.6 km/s |
| Proper motion (μ) | RA: +108.07 mas/yr Dec.: −221.57 mas/yr |
| Parallax (π) | 67.13±1.06 mas |
| Distance | 48.6 ± 0.8 ly (14.9 ± 0.2 pc) |
| Absolute magnitude (MV) | +1.248 |
| Orbit | |
| Period (P) | 3,139.72±0.28 days |
| Semi-major axis (a) | 409.8±0.3 mas |
| Eccentricity (e) | 0.93912±0.00013 |
| Inclination (i) | 130.679±0.067° |
| Longitude of the node (Ω) | 236.86±0.16° |
| Periastron epoch (T) | 2,456,028.2 JD |
| Argument of periastron (ω) (secondary) | 170.21±0.23° |
| Semi-amplitude (K1) (primary) | 12.7±0.2 km/s |
| Semi-amplitude (K2) (secondary) | 33.74±0.35 km/s |
| Details | |
| α Oph A | |
| Mass | 2.20±0.06 M☉ |
| Radius | 2.858±0.015 R☉ (equatorial) 2.388±0.013 (polar) R☉ |
| Luminosity | 31.3±0.96 L☉ |
| Surface gravity (log g) | 3.91 cgs |
| Temperature | 7,569±124 K (equatorial) 9,384±154 (polar) K |
| Rotation | 0.61 days |
| Rotational velocity (v sin i) | 239±12 km/s |
| Age | 0.77±0.03 Gyr |
| α Oph B | |
| Mass | 0.824±0.023 M☉ |
| Other designations | |
| Ras Alhague, Rasalhague, 55 Ophiuchi, BD+12°3252, FK5 656, HD 159561, HIP 86032, HR 6556, SAO 102932. | |
| Database references | |
| SIMBAD | data |
Alpha Ophiuchi (α Ophiuchi, abbreviated Alpha Oph, α Oph), also named Rasalhague /ˈræsəlheɪɡ/, is a binary star and the brightest star in the constellation of Ophiuchus.