BL Crucis

BL Crucis is a red giant and a semiregular variable in the constellation of Crux.^[3] A 5th magnitude star, it is visible to the naked eye under good observing conditions. Three periods have been detected in its light curve, 30.7, 42.3 and 43.6 days.^[1] It is 480 ± 10 light-years distant from Earth.^[2]

BL Crucis

A light curve for BL Crucis, adapted from Tabur et al. (2009)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Crux
Right ascension	12h 27m 28.88s
Declination	−58° 59′ 30.4″
Apparent magnitude (V)	5.38
Characteristics
Spectral type	M4-5III
Variable type	semiregular variable
Astrometry
Radial velocity (Rv)	71.7 ± 0.9 km/s
Proper motion (μ)	RA: -20.027 ± 0.301[2] mas/yr Dec.: 3.586 ± 0.268 [2] mas/yr
Parallax (π)	6.8429±0.1942 mas[2]
Distance	480 ± 10 ly (146 ± 4 pc)
Other designations
HD 108396, HIP 60781, HR 4739, SAO 239960, CD−58° 4560
Database references
SIMBAD	data

In 1969, Olin J. Eggen announced that the star, then called HR 4739, is a variable star.^[4] It was given its variable star designation, BL Crucis, in 1977.^[5]