| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Crux |
| Right ascension | 12h 31m 9.9s |
| Declination | -57° 06′ 48″ |
| Apparent magnitude (V) | 1.59 |
| Characteristics | |
| Spectral type | M4III |
| Apparent magnitude (J) | -1.99 |
| U−B color index | 1.77 |
| B−V color index | 1.60 |
| Astrometry | |
| Radial velocity (Rv) | +20.6 km/s |
| Proper motion (μ) | RA: 27.94 mas/yr Dec.: -264.33 mas/yr |
| Parallax (π) | 37.09 ± 0.67 mas |
| Distance | 88 ± 2 ly (27 ± 0.5 pc) |
| Absolute magnitude (MV) | -0.56 |
| Details | |
| Mass | 3 [1] M☉ |
| Radius | 113 [1] R☉ |
| Luminosity | 1,500 [1] L☉ |
| Temperature | 3,400 [1] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Gamma Crucis (γ Cru, γ Crucis), often called Gacrux, is a red giant star approximately 88 light-years away in the constellation of Crux. Among Portuguese-speaking peoples it is also named "Rubídea" (or Ruby-like), in reference to its color. The star is the third-brightest star in Crux (the Southern Cross) and one of the brightest stars in the night sky. A line from the two "Pointers", Alpha Centauri through Beta Centauri, leads to within a few degrees of this star.
Contents |
Gamma Crucis is a double star, 88 light years distant from Earth. The main star is of apparent magnitude +1.6 and spectral classification M4 III. Its +6.4 magnitude white companion star (spectral classification A3) lies about 2 arcminutes away at an angle of 128 degrees 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. The colour of Gamma Crucis A is a prominent reddish-orange, well in keeping with its spectral classification.
Gacrux has evolved off of the main sequence to become a red giant star, and may even be evolving past the helium-burning stage. It is also semi-variable with a period of about 90 days. The atmosphere is enriched with barium, which is likely due to neutron emission from an undetected white dwarf companion.
Since Gamma Crucis, "Gacrux", is at roughly −60° declination, it is only visible south of the Tropic of Cancer and so lacks an ancient name.
In Chinese, 十字架 (Shí Zì Jià), meaning Cross, refers to an asterism consisting of γ Crucis, α Crucis, β Crucis and δ Crucis.[2] Consequently, γ Crucis itself is known as 十字架一 (Shí Zì Jià yī, English: the First Star of Cross.)[3].
The people of Aranda and Luritja tribe around Hermannsburg, Central Australia named Iritjinga, "The Eagle-hawk", a quadrangular arrangement comprising this star, δ Cru (Palida), γ Cen (Muhilfain) and δ Cen (Ma Wei).[4]
γ Cru is represented in the flags of Australia, New Zealand and Papua New Guinea as one of five stars which comprise the Southern Cross. It is also featured in the flag of Brazil, along with 26 other stars, each of which represents a state. γ Cru represents the State of Bahia[5] .
|
||||||||