CH Crucis
Star in the constellation Crux
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CH Crucis (39 Crucis), also named Lumbung,[13] is a solitary[14] variable star in the southern constellation of Crux. It has the Gould designation 39 G. Crucis.[11] 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.[1] The star is located 844.02 light years distant from the Sun based on parallax, with an uncertainty of −17.35/+18.09 light years.[15] and is drifting further away with a radial velocity of about +12.5 km/s.[1] It is a member of the nearby Sco OB2 association.[16]
  | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Crux[1] |
| Right ascension | 12h 41m 56.56918s[2] |
| Declination | −59° 41′ 08.9544″[2] |
| Apparent magnitude (V) | 4.91[1] |
| Characteristics | |
| Evolutionary stage | subgiant[2] |
| Spectral type | B5III[3] or B6IV[4] |
| U−B color index | −0.37[5] |
| B−V color index | −0.044±0.03[1] |
| Variable type | γ Cas[6] |
| Astrometry | |
| Radial velocity (Rv) | +12.5±2.8[1] km/s |
| Proper motion (μ) | RA: -24.464[2] mas/yr Dec.: -4.226[2] mas/yr |
| Parallax (π) | 3.8643±0.0811 mas[2] |
| Distance | 840 ± 20 ly (259 ± 5 pc) |
| Absolute magnitude (MV) | −2.41[1] |
| Details | |
| Mass | 5.30±0.27[7] M☉ |
| Radius | 11.20±0.22[8] R☉ |
| Luminosity | 1,073[1] L☉ |
| Surface gravity (log g) | 2.90±0.03[8] cgs |
| Temperature | 10,600±106[8] K |
| Rotational velocity (v sin i) | 240[9] km/s |
| Age | 120[10][better source needed] Myr |
| Other designations | |
| Lumbung, 39 Crucis[11], CH Cru, CPD−59°4393, HD 110335, HIP 61966, HR 4823, SAO 240161[12] | |
| Database references | |
| SIMBAD | data |
This is a conventional shell star, which is understood to be a Be star that is being viewed edge-on.[18] Houk (1975) found a stellar classification of B5III,[3] while Hiltner et al. assigned it to B6IV;[4] suggesting it is a B-type star that is evolving off the main sequence.[7]Later literature has also listed the star as B6IVe+sh (Yudin 2001)[19] and B8IV (Arcos et al. 2018),[20] while an older source, Buscombe & Morris (1960) [21]classified it as B7IV and identified it as a spectroscopic binary. indicating some variation in its spectral classification in the literature.
Samus et al. (2017) have tentatively classified it as a Gamma Cassiopeiae variable with a brightness range of 4.88–5.7 mag in the Johnson B band.[6]
CH Crucis has 5.3[7] times the mass of the Sun and 11.2[8] times the Sun's radius. It is radiating 1,073[1] times the luminosity of the Sun from its photosphere at an effective temperature of 10,600 K.[8] It is spinning rapidly with estimates of the projected rotational velocity ranging up to 240 or 250 km/s.[18][9] This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius.[9]
The IAU Working Group on Star Names approved the name Lumbung for this star on 22 February 2026.[13] 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.[22]