Alpha Ophiuchi
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.
| 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) | 3,148.4 days |
| Semi-major axis (a) | 427+20 −13 mas |
| Eccentricity (e) | 0.92±0.03 |
| Inclination (i) | 125+6 −9° |
| Longitude of the node (Ω) | 232±9° |
| Periastron epoch (T) | 2,452,888±53 JD |
| Argument of periastron (ω) (secondary) | 162±14° |
| Details | |
| α Oph A | |
| Mass | 2.40+0.23 −0.37 M☉ |
| Radius | 2.6 R☉ |
| Luminosity | 25.1–25.6 L☉ |
| Surface gravity (log g) | 3.91 cgs |
| Temperature | 7,880–8,050 K |
| Rotational velocity (v sin i) | 240 km/s |
| Age | 0.77±0.03 Gyr |
| α Oph B | |
| Mass | 0.85+0.06 −0.04 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
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