Kappa Crucis (star)
 The centre of NGC 4755, with κ Cru on the left Credit: NASA/ESA and Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain) |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Crux |
| Right ascension | 12h 53m 48.91920s |
| Declination | −60° 22′ 34.4808″ |
| Apparent magnitude (V) | 5.98 |
| Characteristics | |
| Spectral type | B3Ia |
| U−B color index | −0.58 |
| B−V color index | +0.22 |
| Astrometry | |
| Radial velocity (Rv) | -3.5 km/s |
| Proper motion (μ) |
RA: −3.60 mas/yr Dec.: −1.89 mas/yr |
| Parallax (π) | -1.32 ± 0.57mas |
| Distance | 2,600pc |
| Absolute magnitude (MV) | −7.1 |
| Details | |
| Mass | 23.0 M☉ |
| Luminosity | 151,000 L☉ |
| Surface gravity (log g) | 2.25 cgs |
| Temperature | 16,300 K |
| Rotational velocity (v sin i) | 70 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Kappa Crucis (κ Cru, HD 111973) is a spectroscopic binary star in the open cluster NGC 4755, which is also known as the Kappa Crucis Cluster or Jewel Box Cluster.
κ Crucis is one of the brightest members of the open cluster that bears its name, better known as the Jewel Box Cluster. It forms one leg, at bottom right or south, of the prominent letter "A" asterism at the centre of the cluster. The cluster is part of the larger Centaurus OB1 association and lies about 8,500 light years away.
The cluster, and κ Cru itself, is just to the south-east of β Crucis, the lefthand star of the famous Southern Cross.
κ Crucis is a B3 bright supergiant (luminosity class Ia). Radial velocity variations in the spectral lines indicate that it has an unresolved companion star. It is over 100,000 times the luminosity of the sun, partly due to its higher temperature over 26,000 K, and partly to its larger size. The κ Crucis cluster has a calculated age of 11.2 million years.
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