Decrux
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Star Decrux (δ Cru) |
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| Constellation | southern Cross | ||||||||||||||
| Right ascension | 12 h 15 m 8.7 s | ||||||||||||||
| declination | -58 ° 44 ′ 56 ″ | ||||||||||||||
| Apparent brightness | 2.79 likes | ||||||||||||||
| Typing | |||||||||||||||
| B − V color index | −0.23 | ||||||||||||||
| U − B color index | −0.91 | ||||||||||||||
| R − I index | −0.24 | ||||||||||||||
| Spectral class | B2 IV | ||||||||||||||
| Variable star type | Beta Cephei star | ||||||||||||||
| Astrometry | |||||||||||||||
| Radial velocity | (+22.2 ± 2.6) km / s | ||||||||||||||
| parallax | (9.45 ± 0.15) mas | ||||||||||||||
| distance | (345 ± 5) ly (106 ± 2) pc |
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| Visual absolute brightness M vis | −2.3 mag | ||||||||||||||
| Proper movement | |||||||||||||||
| Rec. Share: | (−35.81 ± 0.12) mas / a | ||||||||||||||
| Dec. portion: | (−10.36 ± 0.12) mas / a | ||||||||||||||
| Physical Properties | |||||||||||||||
| Dimensions | 8.5 M ☉ | ||||||||||||||
| radius | 4.9 R ☉ | ||||||||||||||
| Luminosity |
5600 L ☉ |
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| Effective temperature | 22,500 K | ||||||||||||||
| Rotation time | <1.3 days | ||||||||||||||
| Age | <30 million a | ||||||||||||||
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Other names and catalog entries |
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Decrux (also Dekrux) is the proper name of the star δ Crucis (Delta Crucis), created by contracting the Bayer name . Decrux is a sub-giant of the spectral class B2 and has an apparent magnitude of 2.8 mag. It is the faintest of the four stars that make up the Southern Cross . Its distance is about 345 light years , its absolute magnitude −2.3 mag.
Three of these four stars, Alpha , Beta and Delta Crucis, have a similar spectral type and distance, and all belong to a star association, even if they are too far apart to be gravitationally bound.
Like Beta Crucis, Decrux is a variable star of the Beta Cephei type and therefore has small fluctuations in brightness with a period of 3.7 hours. Like many B-stars, it has a high rotation speed, which is at least 194 km / s at the equator, from which a maximum rotation period of 1.3 days is calculated. Due to its strong stellar wind , it loses more than a thousand times as much mass as the sun per time interval. With about 8.5 times the solar mass, it is at the upper end of the spectrum, only to end up as a white dwarf one day .
In Brazil, Decrux is also called Pálida (the pale) and stands for the state of Minas Gerais .