Beta Ophiuchi
 Location of β Ophiuchi (circled) | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 43m 28.35265s[1] |
| Declination | +04° 34′ 02.2955″[1] |
| Apparent magnitude (V) | 2.749[2] (2.75 to 2.77) |
| Characteristics | |
| Spectral type | K2 III[3] |
| U−B color index | +1.253[2] |
| B−V color index | +1.170[2] |
| Variable type | K-type giant[4],[5] |
| Astrometry | |
| Radial velocity (Rv) | –12.53[6] km/s |
| Proper motion (μ) | RA: 41.45[1] mas/yr Dec.: +159.34[1] mas/yr |
| Parallax (π) | 39.85 ± 0.17[1] mas |
| Distance | 81.8 ± 0.3 ly (25.1 ± 0.1 pc) |
| Absolute magnitude (MV) | +0.77 ± 0.04[7] |
| Details | |
| Mass | 1.13[8] M☉ |
| Radius | 12.42 ± 0.13[9] R☉ |
| Luminosity | 63.4 ± 3.2[9] L☉ |
| Surface gravity (log g) | 2.22[3] cgs |
| Temperature | 4,467[8] K |
| Metallicity [Fe/H] | 0.04[3] dex |
| Rotational velocity (v sin i) | 5.4[10] km/s |
| Age | 3.82 ± 1.86[3] Gyr |
| Other designations | |
Beta Ophiuchi (β Oph, β Ophiuchi) is a star in the equatorial constellation of Ophiuchus. It has the traditional names Celbalrai,[11] which comes from the Arabic كلب الراعي kalb al-rā‘ī meaning "shepherd dog".[citation needed] It is also called Cheleb,[11] Kelb Alrai, or sometimes just Alrai. 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 81.8 light-years (25.1 parsecs).[1]
This is a giant star with a stellar classification of K2 III.[3] Although it is only 13% greater in mass than the Sun,[8] it has reached a stage in its evolution where the atmosphere has expanded to about 12 times the Sun's radius and is radiating 63 times the luminosity of the Sun.[9] Its outer envelope is relatively cool with an effective temperature of 4,467 K,[8] giving it the orange hue typical of K-type stars.[13] Like some other K-type giants, β Ophiuchi has been found to vary very slightly (0.02 magnitudes) in brightness.[4],[5]
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]
Planetary system?
Radial velocity variations with a period of 142 days hint about the possible presence of a planetary companion orbiting Beta Ophiuchi. Thus far, no planetary object has been confirmed; while periodic radial pulsations caused by intrinsic stellar variability could explain the observed variations.[5]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| 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
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- ↑ 2.0 2.1 2.2 2.3 Oja, T., "UBV photometry of stars whose positions are accurately known. III", Astronomy and Astrophysics Supplement Series 65 (2): 405–4
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 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
- ↑ 4.0 4.1 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: L157–L160, Bibcode:1996ApJ...464L.157E, doi:10.1086/310108
- ↑ 5.0 5.1 5.2 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
- ↑ 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
- ↑ 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
- ↑ 8.0 8.1 8.2 8.3 Allende Prieto, C.; Lambert, D. L. (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
- ↑ 9.0 9.1 9.2 Berio, P. et al. (November 2011), "Chromosphere of K giant stars. Geometrical extent and spatial structure detection", Astronomy & Astrophysics 535: A59, arXiv:1109.5476, Bibcode:2011A&A...535A..59B, doi:10.1051/0004-6361/201117479
- ↑ 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
- ↑ 11.0 11.1 11.2 Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 301
- ↑ "rho Per -- Semi-regular pulsating Star", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-01-29
- ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16
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