Editing Beta Scorpii

{{Short description|Multi-star system in the constellation of Scorpius}}
{{Starbox begin
| name = β Scorpii
}}
{{Starbox image
| image=
{{Location mark
|image=Scorpius constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=12|mark_link=Beta Scorpii|x=776|y=232
}}
| caption=Location of β Scorpii (circled)
}}
{{Starbox observe 2s
| epoch = [[J2000.0]]
| constell=[[Scorpius]]
| component1 = HR 5984
| ra1        = {{RA|16|05|26.23198}}<ref name=aaa474_2_653/>
| dec1       = {{DEC|–19|48|19.6300}}<ref name=aaa474_2_653/>
| appmag_v1  = 2.62<ref name="Hoffleit1991"/>
| component2 = HR 5985
| ra2        = {{RA|16|05|26.57128}}<ref name=aaa474_2_653/>
| dec2       = {{DEC|–19|48|06.8556}}<ref name=aaa474_2_653/>
| appmag_v2  = 4.92<ref name="Hoffleit1991"/>
}}
{{Starbox character
| component = HR 5984
| class      = B1V<ref name=mk/> {{nowrap|(B0.5IV-V + B1.5V)<ref name=holmgren/>}}
| b-v        = –0.08<ref name=clpl4_99/>
| u-b        = –0.08<ref name=clpl4_99/>
| variable   =
}}
{{Starbox character|no_heading=y
| component = HR 5985
| class      = B2V<ref name=mk/>
| b-v        = –0.02<ref name=clpl4_99/>
| u-b        = –0.70<ref name=clpl4_99/>
| variable   =
}}
{{Starbox astrometry
| component1 = HR 5984
| radial_v   = –1.0<ref name=rgcrv/>
| prop_mo_ra  = –5.20<ref name=aaa474_2_653/>
| prop_mo_dec = –24.04<ref name=aaa474_2_653/>
| parallax   = 8.07
| p_error    = 0.78
| parallax_footnote = <ref name=aaa474_2_653/>
| absmag_v   = –3.92 / –2.60<ref name=catanzaro/>
| component2 = HR 5985
| radial_v2  = –3.6<ref name=rgcrv/>
| prop_mo_ra2 = –5.07<ref name=aaa474_2_653/>
| prop_mo_dec2 = –25.87<ref name=aaa474_2_653/>
| parallax2  = 8.19
| p_error2   = 1.17
| parallax_footnote2 = <ref name=aaa474_2_653/>
| absmag_v2  = –1.83 (Ea: +0.24)<ref name=catanzaro/>
}}
{{Starbox detail
| source = <ref name=catanzaro/>
| component1 = β&nbsp;Sco Aa
| mass       = 15.0
| radius     = 6.3
| luminosity  = 31,600
| temperature = 28,000
| age        =
| metal_fe   =
| rotational_velocity =
| component2   = β&nbsp;Sco Ab
| mass2        = 10.4
| radius2      = 4.0
| luminosity2  = 7,900
| temperature2 = 26,400
}}
{{Starbox detail|no_heading=y
| component1 = β&nbsp;Sco C
| mass       = 8.2
| radius     = 2.9
| luminosity  = 3,200
| temperature = 24,000
| gravity = 3.8
| rotational_velocity = 55
| component2 = β&nbsp;Sco Ea
| mass2       = 3.5
| radius2     = 2.4
| luminosity2  = 126
| temperature2 = 13,000
| gravity2 = 4.2
| rotational_velocity2 = 5
| age_myr2 = 6.3
}}
{{Starbox catalog |
| names = Acrab, Elacrab, Graffias, 8&nbsp;Scorpii, [[Star catalogue#ADS|ADS]]&nbsp;9913, [[Washington Double Star Catalog|WDS]]&nbsp;J16054-1948
| component1 = β<sup>1</sup>&nbsp;Sco
| names1= [[Star catalogue#BD/CD/CPD|BD]]–19&nbsp;4307, [[Henry Draper Catalogue|HD]]&nbsp;144217, [[Hipparcos catalogue|HIP]]&nbsp;78820, [[Star catalogue#BS, BSC, HR|HR]]&nbsp;5984
| component2 = β<sup>2</sup>&nbsp;Sco
| names2 = BD–19&nbsp;4308, HD&nbsp;144218, HIP&nbsp;78821, HR&nbsp;5985
}}
{{Starbox reference
| Simbad = beta+Sco | sn = β Scorpii
| Simbad2 = HR+5984 | sn2 = β<sup>1</sup> Scorpii
| Simbad3 = HR+5985 | sn3 = β<sup>2</sup> Scorpii
}}
{{ Starbox end }}

'''Beta Scorpii''' ('''β Scorpii''', abbreviated '''Beta Sco''', '''β Sco''') is a [[Star system|multiple star system]] in the southern [[zodiac]] [[constellation]] of [[Scorpius]]. It bore the traditional proper name of '''Acrab''' {{IPAc-en|'|æ|k|r|æ|b}},<ref name=Rumrill>{{cite journal
|title=Star Name Pronunciation
|last=Rumrill |first=H. B.
|journal=Publications of the Astronomical Society of the Pacific
|volume=48
|number=283
|date=June 1936
|page=139 |location = San Francisco, California
|doi=10.1086/124681
|bibcode=1936PASP...48..139R |s2cid=120743052 |doi-access=free
}}</ref> though the [[International Astronomical Union]] now regards that name as applying only to the β Scorpii Aa component.

==Components==
Observed through a small telescope, Beta Scorpii appears as a [[binary star]] with a separation between the two components of 13.5&nbsp;[[arcseconds]] and a combined [[apparent magnitude]] of 2.50. This pair, designated β¹ Scorpii and β²&nbsp;Scorpii, form the top branches of a hierarchy of six orbiting components.
<div style="float:left; width:220px; border:solid black 1px; text-align: center; margin: 8px; padding: 4px; font-size: 90%;">
{{chart/start}}
{{chart|border=1| | |  |, |S1| |S1='''Aa''' }}
{{chart|border=0| | |, |( |PA| |PA=Period = 6.82d<br/>a = 1.42 mas }}
{{chart|border=1| | |! |` |S2| |S2='''Ab''' }}
{{chart|border=0| |,|( |PB|  | |PB=Period = 610y<br/>a = 0.30″ }}
{{chart|border=1| |!|` |S3|  | |S3='''B''' }}
{{chart|border=0| |(|PC|  |  | |PC=13.5″&nbsp;separation }}
{{chart|border=1| |!|, |S4|  | |S4='''C''' }}
{{chart|border=0| |`|( |PD|  | |PD=Period = 39y<br/>a = 0.1328″ }}
{{chart|border=1| | |! |, |S5| |S5='''Ea''' }}
{{chart|border=0| | |` |( |PE| |PE=Period = 10.7d }}
{{chart|border=1| | |  |` |S6| |S6='''Eb''' }}
{{chart/end}}
Hierarchy of orbits in the β Scorpii system
</div>
β¹&nbsp;Scorpii, the brighter of the pair, consists of two sub-components, designated β Scorpii A and β Scorpii B, orbiting at an angular separation of 0.3&nbsp;arcseconds with an orbital period of 610 years. β Scorpii A is itself a [[spectroscopic binary]], with the two components designated β Scorpii Aa (also named Acrab<ref name="IAU-LSN"/>) and β Scorpii Ab. They are separated by 1.42&nbsp;[[milliarcsecond]]s and have an orbital period of 6.82 days.<ref name=aj140_3_735/>

β² Scorpii also has two sub-components, designated β Scorpii C and β Scorpii E, orbiting at an angular separation of 0.1328&nbsp;arcseconds with an orbital period of 39 years. β Scorpii E in turn is a spectroscopic binary with components designated β Scorpii Ea and β Scorpii Eb and having an orbital period of 10.7 days.

Component β Scorpii D is the unrelated seventh magnitude star HD 144273, 520" away.<ref name=wds/> Some authors have also referred to component Ab as D.<ref name=vanflandern/>

A companion to component B, β Scorpii G, has been proposed to account for missing mass in the system, but no further evidence of its existence has been found.<ref name=catanzaro/> β Scorpii F refers to a theorised companion to component E.<ref name=vanflandern/>

{{clear left}}

==Nomenclature==

''β Scorpii'' ([[Latinisation of names|Latinised]] to ''Beta Scorpii'') is the star's [[Bayer designation]]; ''β¹'' and ''β² Scorpii'', those of its two components. The designations of the sub-components - ''β Scorpii A'', ''Aa'', ''Ab'', ''B'', ''C'', ''E'', ''Ea'' and ''Eb'' - derive from the convention used by the Washington Multiplicity Catalog (WMC) for [[multiple star system]]s, and adopted by the [[International Astronomical Union]] (IAU).<ref name="planetnaming"/>

Beta Scorpii bore the traditional names ''Acrab'', ''Akrab'' or ''Elacrab'', all deriving from the [[Arabic]] name ({{langx|ar|العقرب}}) ''al-'Aqrab'' 'the Scorpion' for the whole constellation, as well as '''Graffias''' {{IPAc-en|'|g|r|æ|f|i|@|s}},<ref name=Davis44>{{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
|date=1944
|pages = 8–30
|bibcode=1944PA.....52....8D |url=http://adsbit.harvard.edu/full/1944PA.....52....8D
}}</ref> Italian for "the claws", a name it shared with [[Xi Scorpii]].<ref name=graffias/><ref name=allen1899/>

In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN"/> to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire [[multiple star|multiple systems]].<ref name="TriRpt18">{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015-2018) - Star Names |access-date=2018-07-14}}</ref> It approved the name ''Acrab'' for the component ''β Scorpii Aa'' on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>

In [[Chinese astronomy|Chinese]], {{lang|zh|房宿}} ({{lang|zh-Latn|Fáng Xiù}}), meaning ''[[Room (Chinese constellation)|Room]]'', refers to an asterism consisting of both of β<sup>1</sup> Scorpii and β<sup>2</sup> Scorpii, [[Pi Scorpii|π Scorpii]], [[Rho Scorpii|ρ Scorpii]] and [[Delta Scorpii|δ Scorpii]], .<ref>{{in lang|zh}} ''中國星座神話'', written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}.</ref> Consequently, the [[Chinese star names|Chinese name]] for both of β<sup>1</sup> Scorpii and β<sup>2</sup> Scorpii is {{lang|zh|房宿四}} ({{lang|zh-Latn|Fáng Xiù sì}}), "the Fourth Star of Room".<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=2008-10-25 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref>

===Namesake===
[[USS Graffias (AF-29)]] was once a [[United States]] navy ship named after the star.

==Properties==
[[File:Guisard - Milky Way.jpg|thumb|left|upright=1.2|Image of [[Scorpius]] and the [[Milky Way]] with β Scorpii in the top right corner]]
The β Scorpii system is a kinematic member of the Upper Scorpius subgroup of the [[Scorpius–Centaurus association]], a group of thousands of young stars with mean age 11 million years at distance 470 light years (145 parsecs). Analysis of β<sup>1</sup> Scorpii as a single star derived an evolutionary age between 9 and 12 million years,<ref name="Pecaut"/> but analysis of the β Scorpii system as a whole suggest an age closer to 6 million years.<ref name=catanzaro/>

The two components of β Scorpii A are the most massive members of the system, {{solar mass|15|link=y}} and {{solar mass|10}} respectively. The combined spectral type is B1 V. The individual spectral types cannot be clearly measured, but are estimated to be B0.5 and B1.5. Component Aa is evolving slightly away from the [[zero age main sequence]] and its [[luminosity class]] is estimated to be intermediate between [[subgiant]] (IV) and [[main sequence]] (V). Component Ab has a main sequence luminosity class, a temperature of 26,400 K, and a luminosity of {{solar luminosity|7,900}}.

Component B is over 20 times fainter than the combined component A stars and a clear spectral type has not been measured. Its mass is estimated to be approximately {{solar mass|8}}.<ref name=vanflandern/>

Component C has a stellar classification of B2 V and a mass of {{solar mass|8}}. It has an [[effective temperature|effective surface temperature]] of 24,000 K, a radius of {{solar radius|2.9}} and a [[bolometric luminosity]] of {{solar luminosity|3,200}}.

Component E is determined to have a temperature of 13,000 K, radius of {{solar radius|2.4}}, and luminosity of {{solar luminosity|126}}. It is [[Chemically peculiar star|chemically peculiar]], with high abundances of [[manganese]] and [[strontium]]. It is possibly a [[Mercury-manganese star|mercury-manganese]] (HgMn) star, but abundances of other metals are unexpectedly low.<ref name=catanzaro/>

Beta Scorpii is 1.01 degree from the [[ecliptic]] and can be occulted by the [[Moon]] and, very rarely, by [[planet]]s. On December 9, 1906, it was occulted by [[Venus]].<ref name=Koennen1981/> The last [[occultation]] by a planet took place on 13 May 1971, by [[Jupiter]].<ref>{{cite journal |last= Bartholdi |first=P. |author2= Owen, F. |year=1972 |title= The Occultation of Beta Scorpii by Jupiter and Io. II. Io |journal= Astronomical Journal |volume= 77 |pages= 60–65 |bibcode= 1972AJ.....77...60B|doi = 10.1086/111245 }}
</ref>

==Observation==

On 11 December 2019, it had a close conjunction (geocentric separation <1') with [[Mercury (planet)|Mercury]].<ref name="Mus2002">{{cite book |date=2002 |first=Jan |last=Meeus |title=More Mathematical Astronomy Morsels |publisher=Willmann-Bell |isbn=0943396743 |url=https://falakmu.id/khgt/dokumen/More%20mathematical%20astronomy%20morsels%20(Jean%20Meeus)%20(Z-Library).pdf}}</ref>{{rp|167}}

==In culture==
Beta Scorpii appears on the [[flag of Brazil]], symbolising the state of [[Maranhão]].<ref name=abf/>

== References ==
{{Reflist|refs=

<ref name=aaa474_2_653>{{citation | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}</ref>

<ref name=rgcrv>{{cite conference | last=Evans | first=D. S. | date=June 20–24, 1966 | editor1-last=Batten | editor1-first=Alan Henry | editor2-last=Heard | editor2-first=John Frederick | title=The Revision of the General Catalogue of Radial Velocities | volume=30 | pages=57 | conference=IAU Symposium no. 30 | book-title=Determination of Radial Velocities and their Applications  | location=University of Toronto | publisher=International Astronomical Union | bibcode=1967IAUS...30...57E }}</ref>

<ref name=clpl4_99>{{citation | last1=Johnson | display-authors=1 | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99 | year=1966 | bibcode=1966CoLPL...4...99J }}</ref>

<ref name=aj140_3_735>{{citation | last1=Mason | first1=Brian D. | last2=Hartkopf | first2=William I. | last3=Tokovinin | first3=Andrei | title=Binary Star Orbits. IV. Orbits of 18 Southern Interferometric Pairs | journal=The Astronomical Journal | volume=140 | issue=3 | pages=735–743 |date=September 2010 | doi=10.1088/0004-6256/140/3/735 | bibcode=2010AJ....140..735M | doi-access=free }}</ref>

<ref name=allen1899>{{cite book|first=Richard Hinckley|last=Allen|author-link=Richard Hinckley Allen|date=1963|orig-year=1899|title=Star Names: Their Lore and Meaning|page=[https://archive.org/details/starnamestheirlo00alle/page/367 367]|edition=Revised|publisher=[[Dover Publications]]|location=New York|isbn=0-486-21079-0|url-access=registration|url=https://archive.org/details/starnamestheirlo00alle/page/367}}</ref>

<ref name=abf>{{cite web|title=Astronomy of the Brazilian Flag |url=https://flagspot.net/flags/br_astro.html |publisher=FOTW Flags Of The World website | access-date=2017-05-16 }}</ref>

<ref name=catanzaro>{{cite journal|bibcode=2010A&A...509A..21C|title=First spectroscopic analysis of β Scorpii C and β Scorpii E. Discovery of a new Hg ''Mn'' star in the multiple system β Scorpii|journal=Astronomy and Astrophysics|volume=509|pages=A21|last1=Catanzaro|first1=G.|year=2010|doi=10.1051/0004-6361/200913332|doi-access=free}}</ref>

<ref name=wds>{{cite journal | bibcode=2001AJ....122.3466M | doi=10.1086/323920 | title=The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog | journal=The Astronomical Journal | volume=122 | issue=6 | pages=3466 | year=2001 | last1=Mason | first1=Brian D. | last2=Wycoff | first2=Gary L. | last3=Hartkopf | first3=William I. | last4=Douglass | first4=Geoffrey G. | last5=Worley | first5=Charles E. | doi-access=free }}</ref>

<ref name="Hoffleit1991">{{cite web | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HR%202491 | title=Entry for HR 2491 | work=Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) |author1=Hoffleit, D. |author2=Warren Jr., W. H. | date=1991 | publisher=[[Centre de Données astronomiques de Strasbourg|CDS]] }} ID [http://vizier.u-strasbg.fr/viz-bin/Cat?V/50 V/50].</ref>

<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=18 June 2018}}</ref>

<ref name="planetnaming">{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }}</ref>

<ref name=graffias>{{cite journal|bibcode=1924PASP...36..124A|jstor=40692425|title=The Zodiacal Constellation Scorpio|journal=Publications of the Astronomical Society of the Pacific|volume=36|pages=124–130|last1=Aitken|first1=R. G.|year=1924|issue=211|doi=10.1086/123392|doi-access=free}}</ref>

<ref name="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
 | access-date=22 May 2016 | postscript=. }}</ref>

<ref name="Pecaut">{{Cite journal|author1=Mark J. Pecaut |author2=Eric E. Mamajek |author3=Eric J. Bubar  |name-list-style=amp |date=February 2012|title=A Revised Age for Upper Scorpius and the Star Formation History among the F-type Members of the Scorpius–Centaurus OB Association|journal=Astrophysical Journal|volume=746|issue=2|pages=154|arxiv = 1112.1695 |bibcode = 2012ApJ...746..154P |doi = 10.1088/0004-637X/746/2/154 |s2cid=118461108 }}</ref>

<ref name=mk>{{cite journal|bibcode=1981ApJS...45..437A|title=Visual multiples. VII - MK classifications|journal=Astrophysical Journal Supplement Series|volume=45|pages=437|last1=Abt|first1=H. A.|year=1981|doi=10.1086/190719}}</ref>

<ref name=holmgren>{{cite journal|bibcode=1997A&A...322..565H|title=Search for forced oscillations in binaries. II. β Scorpii A. New physical parameters and a search for line profile variability|journal=Astronomy and Astrophysics|volume=322|pages=565|last1=Holmgren|first1=D.|last2=Hadrava|first2=P.|last3=Harmanec|first3=P.|last4=Koubsky|first4=P.|last5=Kubat|first5=J.|year=1997}}</ref>

<ref name=vanflandern>{{cite journal|bibcode=1975ApJ...200...61V|title=Lunar occultations of beta Scorpii in 1975 and 1976|journal=Astrophysical Journal|volume=200|pages=61|last1=Van Flandern|first1=T. C.|last2=Espenschied|first2=P.|year=1975|doi=10.1086/153760|doi-access=free}}</ref>

<ref name=Koennen1981>{{citation
 | title=Planetary occultations of bright stars.
 | last1=Können | first1=G. P. | last2=Van Maanen | first2=J.
 | journal=Journal of the British Astronomical Association
 | volume=91 | pages=148–157 | date=April 1981
 | bibcode=1981JBAA...91..148K }}</ref>

}}

==External links==
*[http://stars.astro.illinois.edu/sow/graffias.html Beta Scorpii by Jim Kaler]
*{{APOD |date=21 May 2009 |title=Image of Beta Scorpii}}

{{Stars of Scorpius}}

[[Category:Bayer objects|Scorpii, Beta]]
[[Category:Spectroscopic binaries]]
[[Category:Multiple star systems|6]]
[[Category:B-type main-sequence stars]]
[[Category:Scorpius]]
[[Category:Stars with proper names|Acrab]]
[[Category:Upper Scorpius]]
[[Category:Flamsteed objects|Scorpii, 08]]
[[Category:Bright Star Catalogue objects|5984 5]]
[[Category:Henry Draper Catalogue objects|144217 8]]
[[Category:Hipparcos objects|078820 1]]
[[Category:Durchmusterung objects]]
[[Category:Mercury-manganese stars]]