Gamma Crucis
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
Crux |
| Right ascension | 12h 31m 9.9s |
| Declination | -57° 06' 45" |
| Apparent magnitude (V) | 1.59 |
| Characteristics | |
| Spectral type | M4 III |
| U-B color index | 1.77 |
| B-V color index | 1.60 |
| Variable type | Semi-regular |
| 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 M☉ |
| Radius | 113 R☉ |
| Luminosity | 1,500 L☉ |
| Temperature | 3,400 K |
| Metallicity | ? |
| Rotation | ? |
| Age | ? years |
| Other designations | |
Gacrux (γ Cru / γ Crucis / Gamma Crucis) is the third-brightest star in constellation Crux (the Southern Cross) and one of the brightest stars in the nighttime sky.
[edit] Physical Properties
Gamma Crucis is a binary 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 companion star (spectral classification A3) lies 25 arcminutes away at an angle of 128 degrees from the main star, and can be observed with binoculars. The colour of Gamma Crucis 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.
[edit] Etymology
Since Gamma Crucis is at roughly −60° declination, it is only visible south of the Tropic of Cancer and likely never received an ancient traditional name. Thus, "Gacrux" is simply a combination of the "Ga" in Gamma plus Crux. It is known as 十字架一 ('First Star of the Cross') in Chinese.
[edit] External links
- Gacrux/Gamma Crucis 2. SolStation. Retrieved on December 5, 2005.
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