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| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
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| Constellation | Ophiuchus |
| Right ascension | 17h 43m 28.353s |
| Declination | +04° 34′ 02.29″ |
| Apparent magnitude (V) | 2.75 to 2.77 |
| Characteristics | |
| Spectral type | K2III |
| U−B color index | 1.24 |
| B−V color index | 1.16 |
| Variable type | K-type giant[1],[2] |
| Astrometry | |
| Radial velocity (Rv) | -12 km/s |
| Proper motion (μ) | RA: -40.67 mas/yr Dec.: 158.80 mas/yr |
| Parallax (π) | 39.78 ± 0.75 mas |
| Distance | 82 ± 2 ly (25.1 ± 0.5 pc) |
| Absolute magnitude (MV) | 0.75 to 0.77 |
| Details | |
| Mass | 1.13 [3] M☉ |
| Radius | 13.2[3] R☉ |
| Luminosity | 62 L☉ |
| Temperature | 4467[3] K |
| Other designations | |
| Data sources: | |
| Hipparcos Catalogue, Bright Star Catalogue (5th rev. ed.), GCVS (4.2),[1],[2] |
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Beta Ophiuchi (β Oph, β Ophiuchi) is a K-type giant star in the constellation Ophiuchus. It has the traditional names Cebalrai (Arabic: كلب الراعي kalb al-rā‘ī '"shepherd dog"), Cheleb, or Kelb Alrai, or sometimes just Alrai. Like some other K-type giants, β Ophiuchi has been found to vary very slightly (0.02 magnitudes) in brightness.[1],[2]
Radial velocity variations with a period of 142 days would hint the possible presence of a planetary companion orbiting Beta Ophiuchi. So far no planetary object has been confirmed; on the other hand pulsation bound to intrinsical variability could explain observed variations.[2]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity |
|---|---|---|---|---|
| b (unconfirmed) | ≥1 MJ | ≥0.6 | 142.3 | ? |
USS Cheleb (AK-138) was a United States Navy Crater class cargo ship named after the star.
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