Gamma Crucis - Physical Properties

Physical Properties

Gacrux has a stellar classification M3.5 III. 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. Although only 30% more massive than the Sun, at this stage the star has expanded to 84 times the Sun's radius. It is radiating 1,500 times the luminosity of the Sun from its expanded outer envelope. With an effective temperature of 3,626 K, the colour of Gamma Crucis is a prominent reddish-orange, well in keeping with its spectral classification. It is a semi-regular variable with multiple periods. (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. 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, which is about 400 light years distant from Earth.