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Beta Ophiuchi

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Beta Ophiuchi
Location of β Ophiuchi (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ophiuchus
Right ascension 17h 43m 28.35191s[1]
Declination +04° 34′ 02.2932″[1]
Apparent magnitude (V) 2.749[2] (2.75 to 2.77)[citation needed]
Characteristics
Spectral type K2 III[3]
U−B color index +1.253[2]
B−V color index +1.170[2]
Astrometry
Radial velocity (Rv)–12.53[4] km/s
Proper motion (μ) RA: −41.793 mas/yr[1]
Dec.: 150.43 mas/yr[1]
Parallax (π)39.2284 ± 0.2027 mas[1]
Distance83.1 ± 0.4 ly
(25.5 ± 0.1 pc)
Absolute magnitude (MV)+0.77 ± 0.04[5]
Details[6]
Mass1.44±0.16[6] – 1.75±0.174[7] M☉
Radius12.17±0.06 R☉
Luminosity57.7±2.9 L☉
Surface gravity (log g)2.33±0.07[7] cgs
Temperature4,559±67 K
Metallicity [Fe/H]0.06±0.04[7] dex
Rotational velocity (v sin i)5.4[8] km/s
Age2.75±0.78 Gyr
Other designations
Cebalrai, Celbalrai, Cheleb[9], Kelb Alrai, Bet Oph, β Oph, β Ophiuchi, 60 Oph, 60 Ophiuchi, BD+04°3489, FK5 665, HD 161096, HIP 86742, HR 6603, SAO 122671[10]
Database references
SIMBADdata

Beta Ophiuchi or β Ophiuchi, also named Cebalrai /ˌsɛbəlˈreɪ.iː/,[11][12] is a star in the equatorial constellation of Ophiuchus. The apparent visual magnitude of this star is 2.7,[2] which is readily visible to the naked eye even from urban skies. The distance to this star can be estimated using parallax measurements, yielding a value of 83.4 light-years (25.6 parsecs) from the Sun.[1]

Nomenclature[edit]

β Ophiuchi (Latinised to Beta Ophiuchi) is the star's Bayer designation.

It bore the traditional names Cebalrai, Celbalrai, Cheleb and Kelb Alrai (or sometimes just Alrai), all derived from the Arabic كلب الراعي kalb al-rā‘ī "the shepherd's dog".[13] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[14] to catalogue and standardize proper names for stars. The WGSN approved the name Cebalrai for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[12]

Namesake[edit]

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

Properties[edit]

This is a giant star with a stellar classification of K2 III.[3] Although it is only 2.75 billion years old, 60% of the solar age, it has reached a stage in its evolution where the atmosphere has expanded to about 12 times the Sun's radius and is radiating 58 times the luminosity of the Sun. Its outer envelope is relatively cool with an effective temperature of 4,559 K,[6] giving it the orange hue typical of K-type stars.[15] Like some other K-type giants, β Ophiuchi has been found to vary very slightly (0.02 magnitudes) in brightness.[16],[17]

Cebalrai is a member of the thin disk population. It is following a low eccentricity orbit through the Milky Way galaxy that carries it between a distance of 27.3–30.9 kly (8.4–9.5 kpc) from the Galactic Center and up to 0.62 kly (0.19 kpc) above or below the galactic plane.[3]

Radial velocity variations with a period of 142 days are likely explained by periodic radial pulsations caused by intrinsic stellar variability.[17]

References[edit]

  1. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d Oja, T. (1986), "UBV photometry of stars whose positions are accurately known. III", Astronomy and Astrophysics Supplement Series, 65 (2): 405–4, Bibcode:1986A&AS...65..405O
  3. ^ a b c Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788, S2CID 16602121
  4. ^ Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304
  5. ^ Carney, Bruce W.; et al. (March 2008), "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars", The Astronomical Journal, 135 (3): 892–906, arXiv:0711.4984, Bibcode:2008AJ....135..892C, doi:10.1088/0004-6256/135/3/892, S2CID 2756572
  6. ^ a b c Baines, Ellyn K.; et al. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal, 155 (1), 30, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b, S2CID 119427037.
  7. ^ a b c Soubiran, C.; Creevey, O. L.; Lagarde, N.; Brouillet, N.; Jofré, P.; Casamiquela, L.; Heiter, U.; Aguilera-Gómez, C.; Vitali, S.; Worley, C.; de Brito Silva, D. (2024-02-01). "Gaia FGK benchmark stars: Fundamental Teff and log g of the third version". Astronomy and Astrophysics. 682: A145. doi:10.1051/0004-6361/202347136. ISSN 0004-6361. Cebalrai's database entry at VizieR.
  8. ^ Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209, S2CID 121883397
  9. ^ Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 301
  10. ^ "rho Per -- Semi-regular pulsating Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-29
  11. ^ Davis, George A. (1944). "The pronunciations, derivations, and meanings of a selected list of star names". Popular Astronomy. 52: 8–30. Bibcode:1944PA.....52....8D.
  12. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016.
  13. ^ Book Of Fixed Stars, Al-Sufi, Bodleian Ms.
  14. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  15. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
  16. ^ Edmonds, Peter D.; Gilliland, Roland L. (June 1996), "K Giants in 47 Tucanae: Detection of a New Class of Variable Stars", Astrophysical Journal Letters, 464 (2): L157–L160, Bibcode:1996ApJ...464L.157E, doi:10.1086/310108
  17. ^ a b Hatzes, Artie P.; Cochran, William D. (September 1996), "The Radial Velocity Variability of the K Giant beta Ophiuchi. II. Long-Period Variations", Astrophysical Journal, 468: 391–397, Bibcode:1996ApJ...468..391H, doi:10.1086/177699
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