Editing Gacrux (section)

== 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.
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