Beta Ophiuchi

Beta Ophiuchi
Ophiuchus constellation map.png
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
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
β Oph, β Ophiuchi, 60 Oph, 60 Ophiuchi, Cebalrai, Cheleb, Kelb Alrai, HR 6603, BD +04°3489, HD 161096, SAO 122671, FK5 665, HIP 86742.
Data sources:
Hipparcos Catalogue,
Bright Star Catalogue (5th rev. ed.),
GCVS (4.2),[1],[2]

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]

Planetary system?

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]

The Beta Ophiuchi system
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity
b (unconfirmed) ≥1 MJ ≥0.6 142.3  ?

Namesakes

USS Cheleb (AK-138) was a United States Navy Crater class cargo ship named after the star.

References

  1. ^ a b c K Giants in 47 Tucanae: Detection of a New Class of Variable Stars, Peter D. Edmonds and Roland L. Gilliland, Astrophysical Journal Letters 464 (June 1996), pp. L157–L160
  2. ^ a b c d The Radial Velocity Variability of the K Giant beta Ophiuchi. II. Long-Period Variations, Artie P. Hatzes and William D. Cochran, Astrophysical Journal 468 (September 1996), pp. 391–397
  3. ^ a b c Allende-Prieto & Lambert (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: masses, radii and effective temperatures". Astronomy and Astrophysics 352: 555–562. arXiv:0809.0359. Bibcode 1999A&A...352..555A. 



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