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}}
}}
{{Starbox character
{{Starbox character
| class = M3.5&nbsp;III<ref name=mnras400_4_1945/>
| type = [[Red giant branch]]
| class = M3.5&nbsp;III<ref name=mnras400_4_1945/>
| appmag_1_passband = J
| appmag_1_passband = J
| appmag_1 = −1.99
| appmag_1 = −1.99
| r-i = <!--R-I color-->
| v-r = <!--V-R color-->
| b-v = +1.59<ref name=ducati/>
| b-v = +1.59<ref name=ducati/>
| u-b = +1.78<ref name=ducati/>
| u-b = +1.78<ref name=ducati/>
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| p_error = 0.18
| p_error = 0.18
| parallax_footnote = <ref name=aaa474_2_653/>
| 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=2024-06-21 |hdl=10278/5003332 |issn=0035-8711}}</ref>
| absmag_v = −0.52<ref name=aaa343_222/>
}}
}}
{{Starbox detail
{{Starbox detail
| mass = 1.5{{±|0.3}}<ref name=mnras254_27/>
| mass = 1.5{{±|0.2}}<ref name="kallinger"/>
| radius = 120<ref name="Rau" />
| radius = 73<ref name="Nielsen2023"/>
| gravity =
| gravity = {{val|0.75|0.02}}<ref name="kallinger"/>
| luminosity = 758<ref name="Rau" />
| luminosity = 830<ref name="kallinger"/>
| temperature = 3,689<ref name="Rau" />
| temperature = {{val|3689|125}}<ref name="kallinger"/>
| metal_fe =
| metal_fe =
| rotational_velocity =
| rotational_velocity =
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{{Starbox reference
{{Starbox reference
| Simbad = HD+108903
| Simbad = HD+108903
| ARICNS = <!--Code-->
}}
}}
{{Starbox end}}
{{Starbox end}}


'''Gacrux'''<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=28 July 2016}}</ref> 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 located at a distance of {{Convert|88.6|ly|pc|abbr=off|lk=on}} from the [[Sun]].<ref name=aaa474_2_653/> It is the nearest M-type [[red giant]] star to the [[Sun]].<ref name=mnras350_1_365/>
'''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 located at a distance of {{Convert|88.6|ly|pc|abbr=off|lk=on}} from the [[Sun]].<ref name=aaa474_2_653/> It is the nearest M-type [[red giant]] star to the [[Sun]].<ref name=mnras350_1_365/>


== Nomenclature ==
== 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]]
[[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]]. Since Gacrux is at roughly −60° [[declination]]. It was known to the [[Ancient Greece|ancient Greeks]] and [[Ancient Rome|Romans]], but oddly in the era lacked a traditional name, and was visible north of 40° [[latitude]] due to the [[precession of equinoxes]]. 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 historical name ''Gacrux'' was coined by astronomer Elijah Hinsdale Burritt (1794-1838).<ref>{{cite web|title=Gacrux/Gamma Crucis 2?|url=http://www.solstation.com/stars2/gacrux2.htm|publisher=SolStation.com|access-date=2011-11-03}}</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.
''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 historical name ''Gacrux'' was coined by astronomer Elijah Hinsdale Burritt (1794-1838).<ref>{{cite web|title=Gacrux/Gamma Crucis 2?|url=http://www.solstation.com/stars2/gacrux2.htm|publisher=SolStation.com|access-date=2011-11-03}}</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}}, {{lang-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>
In [[Chinese language|Chinese]] astronomy, Gamma Crucis was known as {{lang|zh|十字架一}} ({{lang|zh-Latn|Shí Zì Jià yī}}, {{lang-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>
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|}
|}


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=mnras254_27/> at this stage the star has expanded to 120<ref name="Rau">{{Cite journal|last1=Rau|first1=Gioia|last2=Nielsen|first2=Krister E.|last3=Carpenter|first3=Kenneth G.|last4=Airapetian|first4=Vladimir|date=December 2018|title=HST/GHRS Observations of Cool, Low-gravity Stars. VI. Mass-loss Rates and Wind Parameters for M Giants|url=https://ui.adsabs.harvard.edu/abs/2018ApJ...869....1R/abstract|journal=The Astrophysical Journal|language=en|volume=869|issue=1|pages=1|doi=10.3847/1538-4357/aaf0a0|issn=0004-637X|arxiv=1811.10679|bibcode=2018ApJ...869....1R|s2cid=119364960}}</ref> times the [[Solar radius|Sun's radius]]. It is radiating roughly 760<ref name="Rau" /> times the [[Solar luminosity|luminosity of the Sun]] from its expanded [[stellar atmosphere|outer envelope]]. With an [[effective temperature]] of 3,689&nbsp;K,<ref name="Rau" /> 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.)
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.
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.
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== In culture ==
== In culture ==
[[File:Gacrux.jpg|thumb|Gacrux, Gamma Crucis.]]
[[File:Gacrux.jpg|thumb|Gacrux, Gamma Crucis.]]
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) which comprise the [[Southern Cross]].
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/>
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 ==
== See also ==
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<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=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 | bibcode=2009MNRAS.400.1945T |arxiv = 0908.3228 | s2cid=15358380 }}</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 | bibcode=2004MNRAS.350..365I |arxiv = astro-ph/0402326 |s2cid=15830460 }}</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="Ayres2023">{{Cite journal |last=Ayres |first=Thomas |date=2023-05-01 |title=In the Trenches of the Solar-Stellar Connection. VII. Wilson-Bappu 2022 |journal=The Astrophysical Journal Supplement Series |volume=266 |issue=1 |pages=6 |doi=10.3847/1538-4365/acb535 |doi-access=free |bibcode=2023ApJS..266....6A |issn=0067-0049}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/ApJS/266/6&ID=HD%20108903 Gacrux's database entry] at [[VizieR]].</ref>-->
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<ref name=mnras254_27>{{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 }}</ref>


⚫
<!--<ref name=mnras254_27>{{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 }}</ref>
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<ref name=aj112_2274>{{citation | display-authors=1 | last1=Cohen | first1=Martin | last2=Witteborn | first2=Fred C. | last3=Carbon | first3=Duane F. | last4=Davies | first4=John K. | last5=Wooden | first5=Diane H. | last6=Bregman | first6=Jesse D. | title=Spectral Irradiance Calibration in the Infrared. VII.New Composite Spectra, Comparison with Model Atmospheres, and Far-Infrared Extrapolations | journal=Astronomical Journal | volume=112 | page=2274 |date=November 1996 | doi=10.1086/118180 | bibcode=1996AJ....112.2274C }}</ref>
<ref name=aj112_2274>{{citation | display-authors=1 | last1=Cohen | first1=Martin | last2=Witteborn | first2=Fred C. | last3=Carbon | first3=Duane F. | last4=Davies | first4=John K. | last5=Wooden | first5=Diane H. | last6=Bregman | first6=Jesse D. | title=Spectral Irradiance Calibration in the Infrared. VII.New Composite Spectra, Comparison with Model Atmospheres, and Far-Infrared Extrapolations | journal=Astronomical Journal | volume=112 | page=2274 |date=November 1996 | doi=10.1086/118180 | bibcode=1996AJ....112.2274C }}</ref>
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<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=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=aaa343_222>{{citation | last1=Elgarøy | first1=Øystein | last2=Engvold | first2=Oddbjørn | last3=Lund | first3=Niels | title=The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity | journal=Astronomy and Astrophysics | volume=343 | pages=222–228 |date=March 1999 | bibcode=1999A&A...343..222E }}</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=aaa343_222>{{citation | last1=Elgarøy | first1=Øystein | last2=Engvold | first2=Oddbjørn | last3=Lund | first3=Niels | title=The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity | journal=Astronomy and Astrophysics | volume=343 | pages=222–228 |date=March 1999 | bibcode=1999A&A...343..222E }}</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=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>
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<ref name=flag1>{{citation|title=Flag of Brazil|url=http://www.worldafropedia.com/afropedia/Flag_of_Brazil|publisher=World Afropedia}}</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>


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[[Category:Semiregular variable stars]]
[[Category:Semiregular variable stars]]
<!-- Position/Catalogues -->
<!-- Position/Catalogues -->
[[Category:Crux (constellation)]]
[[Category:Crux]]
[[Category:Bayer objects|Crucis, Gamma]]
[[Category:Bayer objects|Crucis, Gamma]]
[[Category:Bright Star Catalogue objects|4763]]
[[Category:Bright Star Catalogue objects|4763]]

Latest revision as of 13:20, 19 August 2024

γ Crucis
Location of Gacrux, γ Crucis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Crux
Right ascension 12h 31m 09.960s[1]
Declination −57° 06′ 47.568″[1]
Apparent magnitude (V) +1.64[2]
Characteristics
Evolutionary stage Red giant branch
Spectral type M3.5 III[3]
Apparent magnitude (J) −1.99
U−B color index +1.78[2]
B−V color index +1.59[2]
Variable type SRV[3]
Astrometry
Radial velocity (Rv)+20.6[4] km/s
Proper motion (μ) RA: +28.23 mas/yr[1]
Dec.: −265.08 mas/yr[1]
Parallax (π)36.83 ± 0.18 mas[1]
Distance88.6 ± 0.4 ly
(27.2 ± 0.1 pc)
Absolute magnitude (MV)−0.68±0.01[5]
Details
Mass1.5±0.2[6] M☉
Radius73[7] R☉
Luminosity830[6] L☉
Surface gravity (log g)0.75±0.02[6] cgs
Temperature3689±125[6] K
Other designations
Gacrux, γ Crucis, CD−56 4504, HD 108903, HIP 61084, HR 4763, SAO 240019, LTT 4752
Database references
SIMBADdata

Gacrux is the third-brightest star in the southern constellation of Crux, the Southern Cross. It has the Bayer designation Gamma Crucis, which is Latinised from γ Crucis and abbreviated Gamma Cru or γ Cru. With an apparent visual magnitude of +1.63,[8] it is the 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 located at a distance of 88.6 light-years (27.2 parsecs) from the Sun.[1] It is the nearest M-type red giant star to the Sun.[9]

Nomenclature

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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 Greeks and 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.[10] The historical name Gacrux was coined by astronomer Elijah Hinsdale Burritt (1794-1838).[11][12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[14] included a table of the first two batches of names approved by the WGSN; which included Gacrux for this star.

In Chinese astronomy, Gamma Crucis was known as 十字架一 (Shí Zì Jià yī, English: the First Star of Cross.).[15]

The people of Aranda and Luritja tribe around Hermannsburg, Central Australia named Iritjinga, "The Eagle-hawk", a quadrangular arrangement comprising Gacrux, Delta Crucis (Imai), Gamma Centauri (Muhilfain) and Delta Centauri (Ma Wei).[16]

Among Portuguese-speaking peoples, especially in Brazil, it is also named Rubídea (or Ruby-like), in reference to its colour.[17]

Physical properties

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Pulsation Periods[3]
Period
(days) 		Amplitude
(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

Gacrux has the MK system stellar classification of M3.5 III.[3] It has 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.[9] Although only 50% more massive than the Sun,[6] at this stage the star has expanded to 73[7] times the Sun's radius. It is radiating roughly 830 times the luminosity of the Sun from its expanded outer envelope.[6] With an effective temperature of 3,689 K,[6] the colour of Gacrux is a prominent reddish-orange, well in keeping with its spectral classification. It is a semi-regular variable with multiple periods.[3] (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.[18] 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,[19] which is about 400 light years distant from Earth.

In culture

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Gacrux, Gamma Crucis.

Gacrux is represented in the flags of Australia, New Zealand, Samoa, and 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.[20] The position of the line passing through Gacrux and Acrux marks the 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.[21]

See also

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References

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  1. ^ a b c d e 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, S2CID 18759600
  2. ^ a b c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  3. ^ a b c d e Tabur, V.; et al. (December 2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–1961, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x, S2CID 15358380
  4. ^ Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
  5. ^ R., Neuhäuser; G., Torres; M., Mugrauer; L., Neuhäuser, D.; J., Chapman; D., Luge; Matteo, Cosci (2022). "Colour evolution of Betelgeuse and Antares over two millennia, derived from historical records, as a new constraint on mass and age". Monthly Notices of the Royal Astronomical Society (in Italian). 516 (1). doi:10.1093/mnra (inactive 2024-06-21). hdl:10278/5003332. ISSN 0035-8711.{{cite journal}}: CS1 maint: DOI inactive as of June 2024 (link) CS1 maint: multiple names: authors list (link)
  6. ^ a b c d e f g Kallinger, T.; Beck, P. G.; Hekker, S.; Huber, D.; Kuschnig, R.; Rockenbauer, M.; Winter, P. M.; Weiss, W. W.; Handler, G.; Moffat, A. F. J.; Pigulski, A.; Popowicz, A.; Wade, G. A.; Zwintz, K. (2019-04-01). "Stellar masses from granulation and oscillations of 23 bright red giants observed by BRITE-Constellation". Astronomy & Astrophysics. 624: A35. arXiv:1902.07531. Bibcode:2019A&A...624A..35K. doi:10.1051/0004-6361/201834514. ISSN 0004-6361.
  7. ^ a b Nielsen, Krister E.; Airapetian, Vladimir S.; Carpenter, Kenneth G.; Rau, Gioia (2023-08-01). "The Advanced Spectral Library: The Evolution of Chromospheric Wind Characteristics from Noncoronal to Hybrid Giant Stars". The Astrophysical Journal. 953 (1): 16. Bibcode:2023ApJ...953...16N. doi:10.3847/1538-4357/acdcf1. ISSN 0004-637X.
  8. ^ Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  9. ^ a b Ireland, M. J.; et al. (May 2004), "Multiwavelength diameters of nearby Miras and semiregular variables", Monthly Notices of the Royal Astronomical Society, 350 (1): 365–374, arXiv:astro-ph/0402326, Bibcode:2004MNRAS.350..365I, doi:10.1111/j.1365-2966.2004.07651.x, S2CID 15830460
  10. ^ Richard Hinckley Allen, "Star Names: Their Lore and Meaning", Dover Press, 1963.
  11. ^ "Gacrux/Gamma Crucis 2?". SolStation.com. Retrieved 2011-11-03.
  12. ^ Lesikar, Arnold V. "Gacrux". Dome Of The Sky. Archived from the original on 2011-09-28. Retrieved 2011-11-03.
  13. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  14. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  15. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived January 30, 2011, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. ^ Raymond Haynes; Roslynn D. Haynes; David Malin; Richard McGee (1996), Explorers of the Southern Sky: A History of Australian Astronomy, Cambridge: Cambridge University Press, p. 8, ISBN 978-0-521-36575-8
  17. ^ da Silva Oliveira, R., "Crux Australis: o Cruzeiro do Sul", Artigos: Planetario Movel Inflavel AsterDomus.
  18. ^ Gomez, A. E.; Luri, X.; Grenier, S.; et al. (March 1997), "Absolute magnitudes and kinematics of barium stars", Astronomy and Astrophysics, 319: 881–885, Bibcode:1997A&A...319..881G
  19. ^ Kaler, James B., "GACRUX (Gamma Crucis)", Stars, University of Illinois, retrieved 2012-03-03
  20. ^ Astronomy of the Brazilian Flag, FOTW Flags Of The World website
  21. ^ Flag of Brazil, World Afropedia
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