Alpha Ophiuchi
 Ras Alhague is the α star in the constellation of Ophiuchus. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 34m 56.1s |
| Declination | +12° 33′ 36″ |
| Apparent magnitude (V) | 2.08 |
| Characteristics | |
| Spectral type | A5 III |
| U−B color index | 0.11 |
| B−V color index | 0.15 |
| Variable type | ? |
| Astrometry | |
| Radial velocity (Rv) | +12.6 km/s |
| Proper motion (μ) | RA: 110.08 mas/yr Dec.: -222.61 mas/yr |
| Parallax (π) | 69.84 ± 0.88 mas |
| Distance | 46.7 ± 0.6 ly (14.3 ± 0.2 pc) |
| Absolute magnitude (MV) | 1.30 |
| Details | |
| Mass | 2–4 M☉ |
| Radius | 2.5 R☉ |
| Luminosity | 29.19 L☉ |
| Temperature | 8,500 K |
| Metallicity | ? |
| Rotation | ? |
| Age | ? years |
| Other designations | |
Alpha Ophiuchi (α Oph / α Ophiuchi) is the brightest star in the constellation Ophiuchus. It also has the traditional name Ras Alhague.
Ras Alhague has an apparent magnitude of +2.08, belongs to the spectral classification A5, and is about 47 light years distant from Earth.
The name Ras Alhague is from the Arabic Ra's al Hawwa', "the Head of the Serpent-charmer."
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