Gamma Crucis

1500 L ☉

Gacrux ( portmanteau of "Gamma" and " Crux ") is the name of the star γ Crucis (Gamma Crucis ) in the constellation of the Southern Cross, the third brightest star he is. Gacrux is only visible from the southern hemisphere. His name seems to have been introduced by the astronomer Elijah Hinsdale Burritt (1794-1838) by contraction of its Bayer designation.

With an apparent magnitude of 1.59 may Gacrux is the 25- brightest stars in the firmament. The distance from Gacrux, a red giant of spectral type M3.5, is about 90 light-years ( Hipparcos database), its absolute brightness like about -0.6. The dimensions of the red giant is estimated to be about 3 solar masses, 110 solar diameter and ( taking into account its infrared ) radiation 1500 times the solar luminosity.

Gacrux is a double star. His companion is a 6.4 like bright blue-white star of spectral type A3, and is located 129 ' from the main component removed. It can be observed already in a prism binoculars. Previously it was assumed that there is a physical, so gravitationally bound binary star, but according to recent observations, the system provides an optical double star is, the companion gamma Crucis B with about 400 light-years away is likely to be more than four times as much as the main star of the sun. Gacrux also has two further optical companion.

The main star is a semi- regular variables, whose brightness varies by a few tenths of a magnitude with a not very constant period of slightly less than 90 days. Through a strong, variable stellar wind he loses mass. He has evolved from a B star of the main sequence to become a red giant and likely today are already at a stage beyond the helium - burning. Since there are barium and other elements in its atmosphere, it should be surrounded by a hitherto unseen white dwarf, which emerged from a more massive (physical) companion. This had been previously swollen into a red giant and shed its outer atmosphere as a planetary nebula, with its heavy elements inside the current main component Gamma Crucis A contaminated.

Weblink

• Gacrux / Gamma Crucis 2, of the SolStation