51 Ophiuchi
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 31m 24.95413s |
| Declination | −23° 57′ 45.5136″ |
| Apparent magnitude (V) | 4.81 |
| Characteristics | |
| Evolutionary stage | pre-main sequence or giant star |
| Spectral type | B9.5IIIe |
| U−B color index | −0.06 |
| B−V color index | +0.00 |
| Astrometry | |
| Radial velocity (Rv) | −12 km/s |
| Proper motion (μ) | RA: +5.24 mas/yr Dec.: −25.72 mas/yr |
| Parallax (π) | 8.04±0.24 mas |
| Distance | 410 ± 10 ly (124 ± 4 pc) |
| Details | |
| Mass | 3.3±0.1 M☉ |
| Radius | 8.08±0.70 (equatorial) 5.66±0.23 (polar) R☉ |
| Surface gravity (log g) | 3.12 cgs |
| Temperature | 9,772 K |
| Metallicity [Fe/H] | −0.25 dex |
| Rotational velocity (v sin i) | 267±5 km/s |
| Age | 0.3 Myr |
| Other designations | |
| c Oph, 51 Oph, CD−23°13412, GC 23320, HD 158643, HIP 85755, HR 6519, SAO 185470 | |
| Database references | |
| SIMBAD | data |
51 Ophiuchi is a single star located approximately 410 light years away from the Sun in the equatorial constellation of Ophiuchus, northwest of the center of the Milky Way. It is visible to the naked eye as a faint, blue-white point of light with an apparent visual magnitude of 4.81. The star is moving closer to the Earth with a heliocentric radial velocity of –12 km/s.
The star has been assigned spectral types of B9.5IIIe and A0 II-IIIe. It is uncertain if it is a pre-main sequence star on the Herbig Ae/Be stage, or is already an evolved giant Be star, as it presents all the characteristics of a typical Be star but also has circumstellar dust that would otherwise indicate a young star. If the star is a Be star, it would be notable for being "a rare, nearby example of a young planetary system just entering the last phase of planet formation". 51 Ophiuchi is about 300,000 years old with 3.3 times the mass of the Sun and a polar radius 5.7 times the Sun's radius. It is radiating three times the Sun's luminosity from its photosphere at an effective temperature of 9,772 K. The star is spinning rapidly with a projected rotational velocity of 267 km/s, close to the critical rotation rate.