Editing Acrux (section)

{{Short description|Star in the constellation Crux}}
{{About|the star|the Christian college|Alphacrucis|research ship|Alpha Crucis (research vessel)}}
{{Starbox begin}}
{{Starbox image
| image=[[File:Acrux kstars.png|250px]]
| caption=The position of Acrux
}}
{{Starbox observe
| pronounce= {{IPAc-en|'|ei|k|r|V|k|s}}{{citation needed|date=May 2022}}
| epoch    = J2000
| constell = [[Crux]]
| ra       = {{RA|12|26|35.89522}}<ref name=aaa474_2_653/>
| dec      = {{DEC|−63|05|56.7343}}<ref name=aaa474_2_653/>
| appmag_v = 0.76<ref name=corben>{{cite journal|bibcode=1966MNSSA..25...44C|title=Photoelectric magnitudes and colours for bright southern stars|journal=Monthly Notes of the Astron. Soc. Southern Africa|volume=25|pages=44|last1=Corben|first1=P. M.|year=1966}}</ref> (1.33 + 1.75)<ref name="Tokovinin1997">{{cite journal|last1=Tokovinin|first1=A. A.|title=MSC - a catalogue of physical multiple stars|journal=Astronomy and Astrophysics Supplement Series|volume=124|issue=1|year=1997|pages=75–84|issn=0365-0138|doi=10.1051/aas:1997181|bibcode = 1997A&AS..124...75T |doi-access=free}}</ref>
}}
{{Starbox character
| class    = B0.5IV + B1V<ref name=houk1979/>
| b-v      = −0.26<ref name=corben/>
| u-b      =
| variable = [[Beta Cephei variable|β Cep]]<ref name=Sharma>{{cite journal|doi=10.1093/mnras/stac1816 |title=Pulsating B stars in the Scorpius–Centaurus Association with TESS |year=2022 |last1=Sharma |first1=Awshesh N. |last2=Bedding |first2=Timothy R. |last3=Saio |first3=Hideyuki |last4=White |first4=Timothy R. |journal=Monthly Notices of the Royal Astronomical Society |volume=515 |issue=1 |pages=828–840 |doi-access=free |arxiv=2203.02582 | bibcode=2022MNRAS.515..828S}}</ref>
}}
{{Starbox astrometry
| radial_v = −11.2 / −0.6<ref name=gcsrv53/>
| prop_mo_ra  = −35.83<ref name=aaa474_2_653/>
| prop_mo_dec = −14.86<ref name=aaa474_2_653/>
| gal_lat  = -00.3627
| gal_lon  = 300.1266
| parallax = 10.13
| p_error  = 0.50
| parallax_footnote = <ref name=aaa474_2_653/>
| absmag_v = −3.77<ref name=kaltcheva>{{cite journal|bibcode= 2014A&A...562A..69K|title= Massive stellar content of the Galactic supershell GSH 305+01-24|journal= Astronomy & Astrophysics|volume= 562|pages= A69|last1= Kaltcheva|first1= N. T.|last2= Golev|first2= V. K.|last3= Moran|first3= K.|year= 2014|doi= 10.1051/0004-6361/201321454|arxiv = 1312.5592 |s2cid= 54222753}}</ref> {{nowrap|(−2.2 + −2.7<ref>{{cite journal|bibcode=1953PASP...65...30V|title=The Twenty Brightest Stars|journal=Publications of the Astronomical Society of the Pacific|volume=65|issue=382|pages=30|last1=Van De Kamp|first1=Peter|year=1953|doi=10.1086/126523|doi-access=free}}</ref>)}}
}}
{{Starbox orbit
| reference=<ref name=Thackeray1980>{{citation
 | last1=Thackeray | first1=A. D. | last2=Wegner | first2=G.
 | title=An improved spectroscopic orbit for α<sup>1</sup> Crucis
 | journal=Monthly Notices of the Royal Astronomical Society
 | volume=191 | issue=2 | pages=217–220 | date=April 1980
 | doi=10.1093/mnras/191.2.217 | bibcode=1980MNRAS.191..217T| doi-access= free}}</ref>
| name=α Crucis Ab
| period_unitless = {{Val|75.7794|0.0037|u=day}}
| eccentricity = {{Val|0.46|0.03}}
| periarg = {{Val|21|6}}
| periastron = {{Val|2417642.3|1.6|fmt=commas|u=JD}}
| k1 = {{Val|41.7|1.2}}
|primary=α Crucis Aa}}
{{Starbox detail
| component1 = α<sup>1</sup>
| metal_fe =
| mass     = 17.80 + 6.05<ref name="Tokovinin1997"/>
| radius   = {{solar radius calculator|type=logLT|1=4.52|logLerr=0.04|2=28840|Terr=0|decimals=2}}<ref name=Sharma/>{{efn | name=radius | Applying the [[Stefan–Boltzmann law]] with a nominal [[sun|solar]] [[effective temperature]] of 5,772&nbsp;[[Kelvin|K]]: 
:<math>\sqrt{\biggl(\frac{5,772}{28,840}\biggr)^4 \cdot 10^{4.52}} = 7.289\ R_\odot</math>.}}
| rotation =
| luminosity = {{val|31,110|3190|2910|fmt=commas}}<ref name=Sharma/>
| rotational_velocity = 124<ref name=Sharma/>
| temperature = 28,840<ref name=Sharma/>
| component2 = α<sup>2</sup>
| metal_fe2 =
| mass2    = 15.52<ref name="Tokovinin1997"/>
| radius2  = {{solar radius calculator|type=AD|0.52|0.099|decimals=2}}<ref name=lang2006/>
| luminosity2 = 16,000<ref name=kaler/>
| rotational_velocity2 = 200<ref name=dravins>{{cite book|bibcode=2010SPIE.7734E..0AD|arxiv=1009.5815|title=Optical and Infrared Interferometry II|series=Proceedings of the SPIE|volume=7734|pages=77340A|last1=Dravins|first1=Dainis|last2=Jensen|first2=Hannes|last3=Lebohec|first3=Stephan|last4=Nuñez|first4=Paul D.|chapter=Stellar intensity interferometry: Astrophysical targets for sub-milliarcsecond imaging |year=2010|doi=10.1117/12.856394|s2cid=55641060}}</ref>
| temperature2 = 28,000<ref name=dravins/>
| age_myr2 = 10.8<ref name=tetzlaff>{{cite journal|bibcode= 2011MNRAS.410..190T|title= A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun|journal= Monthly Notices of the Royal Astronomical Society|volume= 410|issue= 1|pages= 190–200|last1= Tetzlaff|first1= N.|last2= Neuhäuser|first2= R.|last3= Hohle|first3= M. M.|year= 2011|doi= 10.1111/j.1365-2966.2010.17434.x|doi-access= free|arxiv = 1007.4883 |s2cid= 118629873}}</ref>
}}
{{Starbox catalog
| names = {{odlist | B=α Crucis | HIP=60718 | CPD=−62°2745 | WDS=J12266-6306 | CCDM=J12266-6306 }}
| component1 = α<sup>1</sup> Cru
| names1 = {{odlist | name=[[List of proper names of stars|Acrux]] | HR=4730 | HD=108248 | FK5=462 | GC=16952 | name2=[[Gould designation|26&nbsp;G.]]&nbsp;Crucis }}
| component2 = α<sup>2</sup> Cru
| names2 = {{odlist | HR=4731 | HD=108249 | GC=16953 | 2MASS=J12263615-6305571 | name=[[Gould designation|27&nbsp;G.]]&nbsp;Crucis }}
}}
{{Starbox reference
| Simbad=CCDM+J12266-6306AB | sn=α Cru
| Simbad2=*+alf01+Cru | sn2=α<sup>1</sup> Cru
| Simbad3=*+alf02+Cru | sn3=α<sup>2</sup> Cru
}}
{{Starbox end}}

'''Acrux''' is the brightest [[star]] in the southern [[constellation]] of [[Crux]]. It has the [[Bayer designation]] '''α Crucis''', which is [[Latinisation of names|Latinised]] to '''Alpha Crucis''' and abbreviated '''Alpha Cru''' or '''α Cru'''. With a combined [[visual magnitude]] of +0.76, it is the [[list of brightest stars|13th-brightest star]] in the [[night sky]].<!-- Acrux can be passed in brightness by Aldebaran and Enif (ε Pegasi), and Betelgeuse can fall behind Acrux in brightness.--> It is the most southerly star of the [[Asterism (astronomy)|asterism]] known as the Southern Cross and is the southernmost [[first-magnitude star]], 2.3 degrees more southerly than [[Alpha Centauri]].<ref>{{cite book|last1=Bordeleau|first1=André G.|chapter=Federative Republic of Brazil: Constellations in the Breeze|title=Flags of the Night Sky|date=12 August 2013|pages=1–72|doi=10.1007/978-1-4614-0929-8_1|publisher=Springer|location=New York|isbn=978-1-4614-0928-1}}</ref> This system is located at a distance of 321 [[light-year]]s from the [[Sun]].<ref name=aaa474_2_653/><ref name=GSM/>

To the naked eye Acrux appears as a single star, but it is actually a multiple star system containing six components. Through optical [[telescope]]s, Acrux appears as a [[triple star system|triple star]], whose two brightest components are visually separated by about 4 [[arcsecond]]s and are known as Acrux A and Acrux B, α<sup>1</sup> Crucis and α<sup>2</sup> Crucis, or α Crucis A and α Crucis B. Both components are [[B-type star]]s, and are many times more massive and luminous than the Sun. This system was the second ever to be recognized as a binary, in 1685 by a [[Jesuit priest]].<ref>{{cite web | url=https://cfah.org.za/outreach/crux/ | title=A Story about Crux &#124; Centre for Astronomical Heritage (CfAH) }}</ref> α<sup>1</sup> Crucis is itself a [[spectroscopic binary]] with components designated α Crucis Aa (officially named '''Acrux''', historically the name of the entire system)<ref name=Kunitzsch>{{cite book
 |last1=Kunitzsch |first1=Paul
 |last2=Smart |first2=Tim
 |date = 2006 |edition = 2nd rev.
 |title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
 |publisher = Sky Pub |location = Cambridge, Massachusetts
 |isbn = 978-1-931559-44-7
}}</ref><ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=21 November 2016}}</ref> and α Crucis Ab. Its two component stars orbit every 76 days at a separation of about 1 [[astronomical unit]] (AU).<ref name=kaler/> [[HR 4729]], also known as Acrux C, is a more distant companion, forming a triple star through small telescopes. C is also a spectroscopic binary, which brings the total number of stars in the system to at least five.