Beta Monocerotis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Monoceros |
| A | |
| Right ascension | 06h 28m 49.0700s |
| Declination | −07° 01′ 59.025″ |
| Apparent magnitude (V) | 4.60 |
| B | |
| Right ascension | 06h 28m 49.4238s |
| Declination | −07° 02′ 03.876″ |
| Apparent magnitude (V) | 5.00 |
| C | |
| Right ascension | 06h 28m 49.6128s |
| Declination | −07° 02′ 04.763″ |
| Apparent magnitude (V) | 5.32 |
| Characteristics | |
| A | |
| Spectral type | B4Veshell |
| U−B color index | −0.63 |
| B−V color index | −0.10 |
| R−I color index | −0.16 |
| B | |
| Spectral type | B2Vn(e) |
| U−B color index | −0.52 |
| B−V color index | −0.07 |
| C | |
| Spectral type | B3V:nne |
| B−V color index | −0.1 |
| Astrometry | |
| Radial velocity (Rv) | 17.20 km/s |
| Proper motion (μ) | RA: −6.86 mas/yr Dec.: −2.76 mas/yr |
| Parallax (π) | 4.82±1.12 mas |
| Distance | approx. 700 ly (approx. 210 pc) |
| Absolute magnitude (MV) | −1.55 |
| Details | |
| A | |
| Mass | 8.7 M☉ |
| Luminosity | 3,200 L☉ |
| Surface gravity (log g) | 4.06 cgs |
| Temperature | 18,070 K |
| Rotational velocity (v sin i) | 346 km/s |
| Age | 27.5 Myr |
| B | |
| Mass | 6.2 M☉ |
| Luminosity | 1,600 L☉ |
| Rotational velocity (v sin i) | 123 km/s |
| C | |
| Mass | 6 M☉ |
| Luminosity | 1,300 L☉ |
| Rotational velocity (v sin i) | 331 km/s |
| Other designations | |
| β Mon, Beta Monocerotis, Beta Mon, 11 Monocerotis, 11 Mon, STF 919, ADS 5107, CCDM J06288-0702, HIP 30867, WDS 06288-0702A. | |
| A: β1 Monocerotis, β1 Mon, Beta1 Monocerotis, Beta1 Mon, BD−06°1574, GC 8412, HD 45725, HR 2356 | |
| B: BD−06°1575B, HD 45726, HR 2357 | |
| C: BD−06°1575C, HD 45727, HR 2358 | |
| Database references | |
| SIMBAD | data |
| A | |
| B | |
| C | |
Beta Monocerotis (Beta Mon, β Monocerotis, β Mon) is a triple star system in the constellation of Monoceros. To the naked eye, it appears as a single star with an apparent visual magnitude of approximately 3.74, making it the brightest visible star in the constellation. A telescope shows a curved line of three pale blue stars (or pale yellow stars, depending on the scope's focus). William Herschel who discovered it in 1781 commented that it is "one of the most beautiful sights in the heavens". The star system consists of three Be stars, β Monocerotis A, β Monocerotis B, and β Monocerotis C. There is also an additional visual companion star that is probably not physically close to the other three stars.