CH Crucis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Crux |
| Right ascension | 12h 41m 56.56824s |
| Declination | −59° 41′ 08.9564″ |
| Apparent magnitude (V) | 4.91 |
| Characteristics | |
| Spectral type | B5III or B6IV |
| U−B color index | −0.37 |
| B−V color index | −0.044±0.03 |
| Variable type | γ Cas? |
| Astrometry | |
| Radial velocity (Rv) | +12.5±2.8 km/s |
| Proper motion (μ) | RA: -23.987 mas/yr Dec.: -4.110 mas/yr |
| Parallax (π) | 4.2068±0.1651 mas |
| Distance | 780 ± 30 ly (238 ± 9 pc) |
| Absolute magnitude (MV) | −2.41 |
| Details | |
| Mass | 5.30±0.27 M☉ |
| Radius | 11.20±0.22 R☉ |
| Luminosity | 1,073 L☉ |
| Surface gravity (log g) | 2.90±0.03 cgs |
| Temperature | 10,600±106 K |
| Rotational velocity (v sin i) | 240 km/s |
| Age | 120 Myr |
| Other designations | |
| Lumbung, 39 Crucis[11], CH Cru, CPD−59°4393, HD 110335, HIP 61966, HR 4823, SAO 240161 | |
| Database references | |
| SIMBAD | data |
CH Crucis (39 Crucis), also named Lumbung, is a solitary variable star in the southern constellation of Crux. It has the Gould designation 39 G. Crucis. The object is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude that fluctuates around 4.91. The star is located approximately 780 light years distant from the Sun based on parallax, and is drifting further away with a radial velocity of about +12.5 km/s. It is a member of the nearby Sco OB2 association.
This is a conventional shell star, which is understood to be a Be star that is being viewed edge-on. Houk (1975) found a stellar classification of B5III, while Hiltner et al. assigned it to B6IV; suggesting it is a B-type star that is evolving off the main sequence. Samus et al. (2017) have tentatively classified it as a Gamma Cassiopeiae variable that ranges in brightness from magnitude 4.88 down to 5.7.
CH Crucis has 5.3 times the mass of the Sun and 11.2 times the Sun's radius. It is radiating 1,073 times the luminosity of the Sun from its photosphere at an effective temperature of 10,600 K. It is spinning rapidly with estimates of the projected rotational velocity ranging up to 240 or 250 km/s. This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius.
The IAU Working Group on Star Names approved the name Lumbung for this star on 22 February 2026. Lumbung is a constellation from Bali (Indonesia), corresponding to Crux. The term is inherited from Malay, Proto-Malayo-Polynesian, meaning a rice barn or granary. The constellation of Lumbung is attested for ~1300 years in the cultural calendar and associated with Wednesday and the third day of an Oceanic market cycle.