Zeta Crucis
Star in the constellation Crux
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Zeta Crucis is a binary star system in the southern constellation of Crux. Its name is a Bayer designation that is Latinized from ζ Crucis and abbreviated ζ Cru or ζ Cru. This system is visible to the naked eye as a point of light with an apparent visual magnitude of 4.06m. Based on parallax measurements, ζ Crucis is located at a distance of about 353 light-years (108 pc) from the Sun. It is a member of the Lower Centaurus–Crux subgroup of the Scorpius–Centaurus association.[11]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Crux[1] |
| Right ascension | 12h 18m 26.24075s[2] |
| Declination | −64° 00′ 11.1073″[2] |
| Apparent magnitude (V) | 4.04[3] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | B2.5V[4] |
| U−B color index | −0.68[3] |
| B−V color index | −0.17[3] |
| Astrometry | |
| Radial velocity (Rv) | +15.8[5] km/s |
| Proper motion (μ) | RA: −37.431[2] mas/yr Dec.: −6.576[2] mas/yr |
| Parallax (π) | 9.2402±0.1928 mas[2] |
| Distance | 353 ± 7 ly (108 ± 2 pc) |
| Absolute magnitude (MV) | −1.13[1] |
| Details | |
| Mass | 6.4±0.1[6] M☉ |
| Radius | 3.7[2] R☉ |
| Luminosity | 737[1] L☉ |
| Surface gravity (log g) | 3.99[2] cgs |
| Temperature | 18,155[7] K |
| Rotational velocity (v sin i) | 115[8] km/s |
| Age | 19.8[9] Myr |
| Other designations | |
| ζ Cru, CPD−63°2235, HD 106983, HIP 60009, HR 4679, SAO 251841[10] | |
| Database references | |
| SIMBAD | data |
This is a double-lined spectroscopic binary star system.[12] The spectrum matches a B-type main-sequence star with a stellar classification of B2.5 V. It displays pulsational behavior matching a slowly pulsating B-type star and Beta Cephei variable.[13] There is a faint visual companion with an apparent magnitude of 12.49.[14]
A K-type companion star has an angular separation of 0.15″. This corresponds to a projected separation of about 20 au that would yield an orbital period of around 20 years. A common proper motion companion of type M2 is at a separation of around 11′. This would correspond to a projected separation of 60,000 au. It is about 1.5 magnitudes brighter than expected for its temperature, so it is most likely a pre-main-sequence star.[15]