R Coronae Borealis
R Coronae Borealis is a low-mass yellow supergiant star in the constellation of Corona Borealis. It is the prototype of the R Cor Bor class of variable stars, which fade by several magnitudes at irregular intervals. R Coronae Borealis itself normally shines at approximately magnitude 6, just about visible to the naked eye, but at intervals of several months to many years fades to as faint as 15th magnitude. Over successive months it then gradually returns to its normal brightness, giving it the nickname "reverse nova", after the more common type of star which rapidly increases in brightness before fading.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 48m 34.4147s |
| Declination | +28° 09′ 24.295″ |
| Apparent magnitude (V) | 5.71 - 14.8 |
| Characteristics | |
| Spectral type | G0Iep |
| U−B color index | 0.13 |
| B−V color index | 0.60 |
| V−R color index | 0.45 |
| J−H color index | 0.275 |
| J−K color index | 0.800 |
| Variable type | R CrB |
| Astrometry | |
| Radial velocity (Rv) | 27.83 km/s |
| Proper motion (μ) | RA: -2.10 mas/yr Dec.: −11.52 mas/yr |
| Parallax (π) | 0.73 ± 0.27 mas |
| Distance | 1,400 pc |
| Absolute magnitude (MV) | −5 |
| Details | |
| Mass | 0.8-0.9 M☉ |
| Radius | 85 R☉ |
| Luminosity | ~10,000 L☉ |
| Surface gravity (log g) | 0.5 cgs |
| Temperature | 6,750 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
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