Editing Gacrux

{{Short description|Star in the constellation Crux}}
{{Starbox begin
 | name = γ Crucis
}}
{{Starbox image
 | image = [[File:Gacrux.jpg|250px]]
 | caption = Gacrux, γ Crucis
}}
{{Starbox observe
 | pronouce = {{IPAc-en|'|g|æ|k|r|V|k|s}},<ref>{{cite web |url=https://www.starrynighteducation.com/resources_pronunciation.html |title=Audio Pronunciation Guide |date=2009 |website=Starry Night Education |publisher=Simulation Curriculum Corp. |access-date=26 Apr 2019 }}</ref>
 | epoch    = [[J2000.0]]
 | equinox  = [[J2000.0]]
 | constell = [[Crux]]
 | ra       = {{RA|12|31|09.960}}<ref name=aaa474_2_653/>
 | dec      = {{DEC|−57|06|47.57}}<ref name=aaa474_2_653/>
 | appmag_v = +1.64<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|date=2002}}</ref>
}}
{{Starbox character
| type      = [[Red giant branch]]
| class     = M3.5&nbsp;III<ref name=mnras400_4_1945/> 
| appmag_1_passband = J
| appmag_1  = −1.99
| b-v       = +1.59<ref name=ducati/>
| u-b       = +1.78<ref name=ducati/>
| variable  = [[Semiregular variable star|SRV]]<ref name=mnras400_4_1945/>
}}
{{Starbox astrometry
| radial_v  = +20.6<ref name=scfs/>
| prop_mo_ra  = +28.23
| prop_mo_dec = −265.08
| pm_footnote = <ref name=aaa474_2_653/>
| parallax  = 36.83
| p_error   = 0.18
| parallax_footnote = <ref name=aaa474_2_653/>
| absmag_v = {{val|-0.68|0.01}}<ref name=neuhauser>{{Cite journal |last1=R. |first1=Neuhäuser |last2=G. |first2=Torres |last3=M. |first3=Mugrauer |last4=L. |first4=Neuhäuser, D. |last5=J. |first5=Chapman |last6=D. |first6=Luge |last7=Matteo |first7=Cosci |date=2022 |title=Colour evolution of Betelgeuse and Antares over two millennia, derived from historical records, as a new constraint on mass and age |url=https://hdl.handle.net/10278/5003332 |journal=Monthly Notices of the Royal Astronomical Society |language=it |volume=516 |issue=1 |doi=10.1093/mnra |doi-broken-date=1 November 2024 |hdl=10278/5003332 |issn=0035-8711}}</ref>
}}
{{Starbox detail
 | mass = 1.5{{±|0.2}}<ref name="kallinger"/>
 | radius = 73<ref name="Nielsen2023"/>
 | gravity = {{val|0.75|0.02}}<ref name="kallinger"/>
 | luminosity = 830<ref name="kallinger"/>
 | temperature = {{val|3689|125}}<ref name="kallinger"/>
 | metal_fe =
 | rotational_velocity =
 | age_myr =
}}
{{Starbox catalog
 | names = {{odlist | name=Gacrux | CD=−56&nbsp;4504 | B=γ Crucis | Gl=470 | HD=108903 | HIP=61084 | HR=4763 | LTT=4752 | SAO=240019 }}
}}
{{Starbox reference
 | Simbad = HD+108903
}}
{{Starbox end}}

'''Gacrux''' is the third-brightest star in the southern constellation of [[Crux]], the Southern Cross. It has the [[Bayer designation]] '''Gamma Crucis''', which is [[Latinisation of names|Latinised]] from '''γ Crucis''' and abbreviated '''Gamma Cru''' or '''γ Cru'''. With an [[apparent visual magnitude]] of +1.63,<ref name=clpl4/> it is the [[list of brightest stars|26th brightest star]] in the [[night sky]]. A line from the two "Pointers", [[Alpha Centauri]] through [[Beta Centauri]], leads to within 1° north of this star. Using [[parallax]] measurements made during the [[Hipparcos]] mission, it is {{Convert|88.6|ly|pc|abbr=off|lk=on}} distant.<ref name=aaa474_2_653/> It is the nearest M-type [[red giant]] star.<ref name=mnras350_1_365/>

== Nomenclature ==
[[File:Deep Crux wide field with fog.jpg|thumb|left|The constellation [[Crux]], with the reddish star Gacrux at the top of the constellation (north) in this image]]
''γ Crucis'' (Latinised to ''Gamma Crucis'') is the star's [[Bayer designation]]. Gacrux is currently at roughly 60° south [[declination]]. It was known and visible to the [[Ancient Greece|ancient Greeks]] and [[Ancient Rome|Romans]] as it was visible north of 40° [[latitude]] because of the [[precession of equinoxes]]. Oddly, it lacked a traditional name. The astronomer [[Ptolemy]] counted it as part of the constellation of [[Centaurus]].<ref>Richard Hinckley Allen, "Star Names: Their Lore and Meaning", Dover Press, 1963.</ref> The name ''Gacrux'' was coined by astronomer Elijah Hinsdale Burritt (1794-1838) as a contraction of the Bayer designation.<ref>{{cite web|title=Gacrux/Gamma Crucis 2?|url=http://www.solstation.com/stars2/gacrux2.htm|publisher=SolStation.com|access-date=2011-11-03 |archive-url=https://web.archive.org/web/20230407220320/http://www.solstation.com/stars2/gacrux2.htm |archive-date=7 April 2023 |url-status=dead}}</ref><ref>{{cite web|last=Lesikar|first=Arnold V.|title=Gacrux|url=http://domeofthesky.com/clicks/gacrux.html|publisher=Dome Of The Sky|access-date=2011-11-03|url-status=dead|archive-url=https://web.archive.org/web/20110928143206/http://domeofthesky.com/clicks/gacrux.html|archive-date=2011-09-28}}</ref> In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> included a table of the first two batches of names approved by the WGSN, which included ''Gacrux'' for this star.

In [[Chinese language|Chinese]] astronomy, Gamma Crucis was known as {{lang|zh|十字架一}} ({{lang|zh-Latn|Shí Zì Jià yī}}, {{langx|en|the First Star of Cross}}).<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_e_g.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive |url=https://web.archive.org/web/20110130063007/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_e_g.htm |date=January 30, 2011 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref>

The people of [[Aranda people|Aranda]] and [[Luritja]] tribe around  [[Hermannsburg, Northern Territory|Hermannsburg]], [[Central Australia]] named ''Iritjinga'', "The Eagle-hawk", a quadrangular arrangement comprising Gacrux, [[Delta Crucis]] (Imai), [[Gamma Centauri]] (Muhilfain) and [[Delta Centauri]] (Ma Wei).<ref>{{citation|author1=Raymond Haynes|author2=Roslynn D. Haynes|author3=David Malin|author4=Richard McGee|title=Explorers of the Southern Sky: A History of Australian Astronomy|url=https://books.google.com/books?id=XoeiJxMmXZ8C|year=1996|publisher=Cambridge University Press|location=Cambridge|isbn=978-0-521-36575-8|page=8}}</ref> To the Boorong clan of the [[Wergaia]], this star is known as Bunya.<ref name="Hamacher2010"/><ref>{{cite web |url=https://nameexoworlds.iau.org/2022naming-rules |title=NameExoWorlds 2022 Naming Rules |publisher=[[International Astronomical Union|IAU]] |access-date=26 April 2025}}</ref>

Among Portuguese-speaking peoples, especially in Brazil, it is also named ''Rubídea'' (or Ruby-like), in reference to its colour.<ref>da Silva Oliveira, R., [https://web.archive.org/web/20131206102730/http://www.asterdomus.com.br/Artigo_crux_australis.htm "Crux Australis: o Cruzeiro do Sul"], Artigos: Planetario Movel Inflavel AsterDomus.</ref>

== Physical properties ==
{| class="wikitable" style="float: left; text-align: center; margin: 0.5em;"
|+ ''Pulsation Periods''<ref name=mnras400_4_1945/>
! Period<br />(days)
! Amplitude<br />(magnitude)
|-
| 12.1 || 0.016
|-
| 15.1 || 0.027
|-
| 16.5 || 0.016
|-
| 54.8 || 0.026
|-
| 82.7 || 0.015
|-
| 104.9 || 0.016
|}
[[File:GamCruLightCurve.png|thumb|right|A [[light curve]] for Gamma Crucis, plotted from data published by Tabur ''et al.''<ref name=mnras400_4_1945/>]]

Gacrux has the MK system [[stellar classification]] of M3.5&nbsp;III.<ref name=mnras400_4_1945/> It has [[stellar evolution|evolved]] off of the [[main sequence]] to become a [[red giant]] star, but is most likely on the [[red giant branch]] rather than the [[asymptotic giant branch]].<ref name=mnras350_1_365/> Although only 50% more massive than the Sun,<ref name="kallinger"/> at this stage the star has expanded to 73<ref name="Nielsen2023"/> times the [[Solar radius|Sun's radius]]. It is radiating roughly 830 times the [[Solar luminosity|luminosity of the Sun]] from its expanded [[stellar atmosphere|outer envelope]].<ref name="kallinger"/> With an [[effective temperature]] of 3,689&nbsp;K,<ref name="kallinger"/> the colour of Gacrux is a prominent reddish-orange, well in keeping with its spectral classification. It is a [[Semiregular variable star|semi-regular variable]] with multiple periods.<ref name=mnras400_4_1945/> (See table at left.)

The atmosphere of this star is enriched with [[barium]], which is usually explained by the transfer of material from a more evolved companion. Typically this companion will subsequently become a [[white dwarf]].<ref name=aaa319_881/> However, no such companion has yet been detected. A +6.4 magnitude companion star lies about 2 arcminutes away at a [[position angle]] of 128° from the main star, and can be observed with [[binoculars]]. But it is only an optical companion,<ref name=kaler/> which is about 400 light years distant from Earth.
{{clear left}}
== In culture ==
Gacrux is represented in the flags of [[flag of Australia|Australia]], [[flag of New Zealand|New Zealand]], [[flag of Samoa|Samoa]], and [[flag of Papua New Guinea|Papua New Guinea]] as one of five stars (four in the case of New Zealand) that compose the [[Southern Cross]].

It is also featured on the [[flag of Brazil]], along with 26 other stars, each of which represents a state. Gacrux represents the State of [[Bahia]].<ref name=flag/> The position of the line passing through Gacrux and [[Acrux]] marks the [[Meridian (astronomy)|local meridian]] of the sky observed from [[Rio de Janeiro]], at 8:30 am on 15 November 1889, the time when the republic was formally ratified.<ref name=flag1/>

== See also ==
* [[Aldebaran]]
* [[Betelgeuse]]

{{clear}}
==References==
{{Reflist|refs=

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

<ref name=scfs>{{citation | display-authors=1 | title=Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions | journal=Veröff. Astron. Rechen-Inst. Heidelb | volume=35 | last1=Wielen | first1=R. | last2=Schwan | first2=H. | last3=Dettbarn | first3=C. | last4=Lenhardt | first4=H. | last5=Jahreiß | first5=H. | last6=Jährling | first6=R. | publisher=Astronomisches Rechen-Institut Heidelberg | issue=35 | pages=1 | date=1999 | bibcode=1999VeARI..35....1W }}</ref>

<ref name=clpl4>{{cite journal | display-authors=1 | last1=Johnson | 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 | date=1966 | bibcode=1966CoLPL...4...99J }}</ref>

<ref name=mnras400_4_1945>{{citation | display-authors=1 | last1=Tabur | first1=V. | last2=Bedding | first2=T. R. | last3=Kiss | first3=L. L. | last4=Moon | first4=T. T. | last5=Szeidl | first5=B. | last6=Kjeldsen | first6=H. | title=Long-term photometry and periods for 261 nearby pulsating M giants | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=400 | issue=4 | pages=1945–1961 |date=December 2009 | doi=10.1111/j.1365-2966.2009.15588.x | doi-access=free | bibcode=2009MNRAS.400.1945T |arxiv = 0908.3228 | s2cid=15358380 }}</ref>

<ref name=mnras350_1_365>{{citation | display-authors=1 |last1=Ireland | first1=M. J. | last2=Tuthill | first2=P. G. | last3=Bedding | first3=T. R. | last4=Robertson | first4=J. G. | last5=Jacob | first5=A. P. | title=Multiwavelength diameters of nearby Miras and semiregular variables | journal=Monthly Notices of the Royal Astronomical Society | volume=350 | issue=1 | pages=365–374 |date=May 2004 | doi=10.1111/j.1365-2966.2004.07651.x |doi-access=free | bibcode=2004MNRAS.350..365I |arxiv = astro-ph/0402326 |s2cid=15830460 }}</ref>

<ref name=aaa319_881>{{citation| display-authors=3| last1=Gomez | first1=A. E.| last2=Luri | first2=X.| last3=Grenier | first3=S.| last4=Prevot | first4=L.| last5=Mennessier | first5=M. O.| last6=Figueras | first6=F.| last7=Torra | first7=J.| title=Absolute magnitudes and kinematics of barium stars | journal=Astronomy and Astrophysics | volume=319 | pages=881–885 |date=March 1997 | bibcode=1997A&A...319..881G }}</ref>

<ref name="Nielsen2023">{{Cite journal |last1=Nielsen |first1=Krister E. |last2=Airapetian |first2=Vladimir S. |last3=Carpenter |first3=Kenneth G. |last4=Rau |first4=Gioia |date=2023-08-01 |title=The Advanced Spectral Library: The Evolution of Chromospheric Wind Characteristics from Noncoronal to Hybrid Giant Stars |journal=The Astrophysical Journal |volume=953 |issue=1 |pages=16 |doi=10.3847/1538-4357/acdcf1 |doi-access=free |bibcode=2023ApJ...953...16N |issn=0004-637X}}</ref>

<ref name=kaler>{{citation | first1=James B. | last1=Kaler | title=GACRUX (Gamma Crucis) | work=Stars | publisher=[[University of Illinois]] | url=http://stars.astro.illinois.edu/sow/gacrux.html | access-date=2012-03-03 }}</ref>

<ref name=flag>{{citation|title=Astronomy of the Brazilian Flag |url=https://flagspot.net/flags/br_astro.html |publisher=FOTW Flags Of The World website }}</ref>

<ref name=flag1>{{citation|title=Flag of Brazil|url=http://www.worldafropedia.com/afropedia/Flag_of_Brazil|publisher=World Afropedia}}</ref>

<ref name="kallinger">{{Cite journal |last1=Kallinger |first1=T. |last2=Beck |first2=P. G. |last3=Hekker |first3=S. |last4=Huber |first4=D. |last5=Kuschnig |first5=R. |last6=Rockenbauer |first6=M. |last7=Winter |first7=P. M. |last8=Weiss |first8=W. W. |last9=Handler |first9=G. |last10=Moffat |first10=A. F. J. |last11=Pigulski |first11=A. |last12=Popowicz |first12=A. |last13=Wade |first13=G. A. |last14=Zwintz |first14=K. |date=2019-04-01 |title=Stellar masses from granulation and oscillations of 23 bright red giants observed by BRITE-Constellation |url=https://www.aanda.org/articles/aa/abs/2019/04/aa34514-18/aa34514-18.html |journal=Astronomy & Astrophysics |language=en |volume=624 |pages=A35 |doi=10.1051/0004-6361/201834514 |arxiv=1902.07531 |bibcode=2019A&A...624A..35K |issn=0004-6361}}</ref>

<ref name="Hamacher2010">{{cite journal |last1=Hamacher |first1=Duane W. |last2=Frew |first2=David J. |year=2010 |title=An aboriginal Australian record of the great eruption of Eta Carinae |journal=Journal of Astronomical History and Heritage |volume=13 |issue=3 |pages=220–234 |arxiv=1010.4610 |bibcode=2010JAHH...13..220H |s2cid=118454721 |doi=10.3724/SP.J.1440-2807.2010.03.06}}</ref>

}}

==Further reading==
* {{citation | last1=Murdoch | first1=Kaylene | last2=Clark | first2=M. | last3=Hearnshaw | first3=J. B. | title=The radial-velocity variability of Gamma Crucis | journal=Monthly Notices of the Royal Astronomical Society | volume=254 | pages=27–29 |date=January 1992 | bibcode=1992MNRAS.254...27M | doi=10.1093/mnras/254.1.27| doi-access=free }}

{{Stars of Crux}}
{{Authority control}}
{{Sky|12|31|09.95961|-|57|06|47.5684}}

{{DEFAULTSORT:Gacrux}}
<!-- Properties -->
[[Category:M-type giants]]
[[Category:Barium stars]]
[[Category:Semiregular variable stars]]
<!-- Position/Catalogues -->
[[Category:Crux]]
[[Category:Bayer objects|Crucis, Gamma]]
[[Category:Bright Star Catalogue objects|4763]]
[[Category:Durchmusterung objects|CD-56 04504]]
[[Category:Gliese and GJ objects|0470]]
[[Category:Henry Draper Catalogue objects|108903]]
[[Category:Hipparcos objects|061084]]
[[Category:Stars with proper names|Gacrux]]