BL Crucis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Crux |
| Right ascension | 12h 27m 28.88s |
| Declination | −58° 59′ 30.4″ |
| Apparent magnitude (V) | 5.43 |
| Characteristics | |
| Evolutionary stage | AGB |
| Spectral type | M4/5III |
| Variable type | SR |
| Astrometry | |
| Radial velocity (Rv) | 71.7±0.9 km/s |
| Proper motion (μ) | RA: −19.294 mas/yr Dec.: +4.680 mas/yr |
| Parallax (π) | 6.8429±0.1942 mas |
| Distance | 480 ± 10 ly (146 ± 4 pc) |
| Absolute magnitude (MV) | −0.28 |
| Details | |
| Mass | 3.6 M☉ |
| Radius | 106 R☉ |
| Luminosity | 1,234 L☉ |
| Surface gravity (log g) | 1.94 cgs |
| Temperature | 3,320 K |
| Metallicity [Fe/H] | −0.33 dex |
| Other designations | |
| CD−58°4560, HD 108396, HIP 60781, HR 4739, SAO 239960 | |
| Database references | |
| SIMBAD | data |
BL Crucis is a red giant and a semiregular variable in the constellation of Crux. A 5th magnitude star, it is visible to the naked eye under good observing conditions. It is 480±10 light-years distant from Earth.
In 1969, Olin J. Eggen announced that the star, then called HR 4739, is a variable star. It was given its variable star designation, BL Crucis, in 1977. Three periods have been detected in its light curve, 30.7, 42.3 and 43.6 days. The maximum amplitude of variation is 0.35 magnitudes.
An aging red giant, BL Crucis is on the asymptotic giant branch having exhaust both its core hydrogen and core helium. It now fuses hydrogen and helium in separate shells outside the core.