Beta Ophiuchi
{{Short description|Orange giant star in the constellation Ophiuchus}}
{{Starbox begin}}
{{Starbox image
| image =
{{Location mark
| image=Ophiuchus IAU.svg
| float=center | width=250 | position=right
| mark=Red circle.svg | mark_width=10 | mark_link=ι Exa
| x%=41.8 | y%=25.8
}}
| caption=Location of β Ophiuchi (circled)
}}
{{Starbox observe
| dec = {{DEC|+04|34|02.2932}}
| appmag_v = 2.749 (2.75 to 2.77){{Citation needed |date=June 2024}}
| constell = Ophiuchus
}}
{{Starbox character
}}
{{Starbox astrometry
| prop_mo_ra = {{val|-41.793}}
| prop_mo_dec = {{val|150.43}}
| parallax = 39.2284
| p_error = 0.2027
| absmag_v = {{nowrap|+0.77 ± 0.04}}
}}
{{Starbox detail
| mass = {{val|1.44|0.16}}{{snd}}{{val|1.75|0.174}}
| radius = {{val|12.17|0.06}}
| luminosity = {{val|57.7|2.9}}
| temperature = {{val|4559|67|fmt=commas}}
| metal_fe = {{val|0.06|0.04}}
| age_gyr = {{val|2.75|0.78}}
}}
{{Starbox catalog
| names = {{odlist | name=Cebalrai | name2=Celbalrai | name3=Cheleb | name4=Kelb Alrai | B=Bet Oph, β Oph, β Ophiuchi | F=60 Oph, 60 Ophiuchi | BD=+04°3489 | FK5=665 | HD=161096 | HIP=86742 | HR=6603 | SAO=122671 }}
}}
{{Starbox reference
|Simbad=bet+Oph
}}
{{Starbox end}}
Beta Ophiuchi or β Ophiuchi, also named Cebalrai {{IPAc-en|,|s|E|b|@l|'|r|ei|.|iː}},{{cite journal
|title=The pronunciations, derivations, and meanings of a selected list of star names
|last=Davis |first=George A.
|journal=Popular Astronomy
|volume=52
|number=
|date=1944
|pages = 8–30
|bibcode=1944PA.....52....8D |url=http://adsbit.harvard.edu/full/1944PA.....52....8D
}}{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |accessdate=28 July 2016}} is a star in the equatorial constellation of Ophiuchus. The apparent visual magnitude of this star is 2.7, 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 {{Convert|83.4|ly|pc|abbr=off|lk=on}} from the Sun.
Nomenclature
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".{{citation|
url=https://digital.bodleian.ox.ac.uk/inquire/Discover/Search/#/?p=c+0,t+,rsrs+0,rsps+10,fa+,so+ox%3Asort%5Easc,scids+,pid+c1caa84c-f6d2-483f-9eb4-2439cccdc801,vi+62392615-fb52-4c0c-bf97-ed5153a1d509|
title=Book Of Fixed Stars, Al-Sufi, Bodleian Ms.
}} In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN){{citation
| url=https://www.iau.org/science/scientific_bodies/working_groups/280/
| title=IAU Working Group on Star Names (WGSN)
| publisher=International Astronomical Union
| accessdate=22 May 2016 | postscript=. }} 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.
=Namesake=
USS Cheleb (AK-138) was a United States Navy Crater class cargo ship named after the star.
Properties
This is a giant star with a stellar classification of K2 III. 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, giving it the orange hue typical of K-type stars. Like some other K-type giants, β Ophiuchi has been found to vary very slightly (0.02 magnitudes) in brightness.,
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 {{Convert|27.3|–|30.9|kly|kpc|abbr=on|lk=on}} from the Galactic Center and up to {{Convert|0.62|kly|kpc|abbr=on}} above or below the galactic plane.
Radial velocity variations with a period of 142 days are likely explained by periodic radial pulsations caused by intrinsic stellar variability.
References
{{Reflist|30em|refs=
| title=Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer
| last1=Baines | first1=Ellyn K. | last2=Armstrong | first2=J. Thomas | last3=Schmitt | first3=Henrique R. | last4=Zavala | first4=R. T. | last5=Benson | first5=James A. | last6=Hutter | first6=Donald J. | last7=Tycner | first7=Christopher | last8=Belle | first8=Gerard T. van
| display-authors=1 | journal=The Astronomical Journal
| volume=155 | at=30 | year=2018 | issue=1 | postscript=.
| arxiv=1712.08109 | bibcode=2018AJ....155...30B
| doi=10.3847/1538-3881/aa9d8b | s2cid=119427037 | doi-access=free }}
{{Cite DR3|4473334474604992384}}
{{Cite journal |last1=Soubiran |first1=C. |last2=Creevey |first2=O. L. |last3=Lagarde |first3=N. |last4=Brouillet |first4=N. |last5=Jofré |first5=P. |last6=Casamiquela |first6=L. |last7=Heiter |first7=U. |last8=Aguilera-Gómez |first8=C. |last9=Vitali |first9=S. |last10=Worley |first10=C. |last11=de Brito Silva |first11=D. |date=2024-02-01 |title=Gaia FGK benchmark stars: Fundamental Teff and log g of the third version |url=https://ui.adsabs.harvard.edu/abs/2024A&A...682A.145S |journal=Astronomy and Astrophysics |volume=682 |pages=A145 |doi=10.1051/0004-6361/202347136 |bibcode=2024A&A...682A.145S |issn=0004-6361}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/A%2BA/682/A145&recno=164 Cebalrai's database entry] at VizieR.
{{citation |title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |accessdate=2012-01-16 |url-status=dead |archiveurl=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archivedate=2012-03-18 }}
{{citation | title=rho Per -- Semi-regular pulsating Star | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Beta+Ophiuchi | accessdate=2012-01-29 }}
}}
{{Stars of Ophiuchus}}
{{DEFAULTSORT:Beta Ophiuchi}}