BG Crucis
Star system in the Crux constellation
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BG Crucis is a suspected binary star[11] system in the southern constellation of Crux. It is visible to the naked eye as a faint yellow-white hued point of light with an apparent visual magnitude of about 5. The system is located at a distance of approximately 1,830 light years from the Sun based on parallax, and is drifting closer with a radial velocity of −19 km/s.[6]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Crux[2] |
| Right ascension | 12h 31m 40.33011s[3] |
| Declination | −59° 25′ 26.1224″[3] |
| Apparent magnitude (V) | 5.34 - 5.58[4] |
| Characteristics | |
| Spectral type | F7Ib/II[5] (F5Ib - G0p)[4] |
| B−V color index | 0.622±0.012[2] |
| Astrometry | |
| Radial velocity (Rv) | −19.3±2.2[6] km/s |
| Proper motion (μ) | RA: −12.689[3] mas/yr Dec.: −4.110[3] mas/yr |
| Parallax (π) | 1.7777±0.0873 mas[3] |
| Distance | 1,830 ± 90 ly (560 ± 30 pc) |
| Absolute magnitude (MV) | −2.63[2] |
| Details | |
| Mass | 4.3[7] or 6.3±0.5[8] M☉ |
| Radius | 39.30+2.82 −3.23[3] R☉ |
| Luminosity | 1,033.93[2] L☉ |
| Surface gravity (log g) | 2.15[7] cgs |
| Temperature | 6,253±30[7] K |
| Rotational velocity (v sin i) | 22.0±1.8[9] km/s |
| Age | 63.7±15.8[8] Myr |
| Other designations | |
| BG Cru, AAVSO 1226-58, CD−58° 4603, HD 108968, HIP 61136, HR 4768, SAO 180937, G 35 Cru[10] | |
| Database references | |
| SIMBAD | data |
The visible component is a supergiant star that pulsates between spectral types F5Ib and G0p.[4] It is a small amplitude[12] classical Cepheid variable with an apparent magnitude ranges from 5.34 down to 5.58 over a period of 3.3428 days.[4] On the Hertzsprung–Russell diagram of temperature versus luminosity, it is located near the blue (hotter) edge of the Cepheid instability strip. Models indicate the cepheid region is relatively small in this star, so there are no shock waves produced as a result of the instability.[7]
BG Crucis is 64[8] million years old with four[7] to six[8] times the mass of the Sun. Having exhausted the supply of hydrogen at its core, it has expanded to 39[3] times the Sun's radius. It is radiating over a thousand[2] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 6,253 K.[7]