Delta Ophiuchi
Delta Ophiuchi (δ Ophiuchi, abbreviated Delta Oph, δ Oph), formally named Yed Prior /ˌjɛd ˈpraɪər/, is a star in the constellation of Ophiuchus. It forms a naked-eye optical double with Epsilon Ophiuchi (named Yed Posterior). The apparent visual magnitude is 2.75, making this a third-magnitude star and the fourth-brightest in the constellation. Parallax measurements from the Hipparcos spacecraft yield a distance estimate of approximately 171 light-years (52 parsecs) from the Sun (Epsilon Ophiuchi is approximately 108 light-years (33 parsecs)).
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 16h 14m 20.73853s |
| Declination | –03° 41′ 39.5612″ |
| Apparent magnitude (V) | 2.75 |
| Characteristics | |
| Evolutionary stage | AGB |
| Spectral type | M0.5 III |
| U−B color index | +1.96 |
| B−V color index | +1.59 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | –19.9 km/s |
| Proper motion (μ) | RA: –47.54 mas/yr Dec.: –142.73 mas/yr |
| Parallax (π) | 19.06 ± 0.16 mas |
| Distance | 171 ± 1 ly (52.5 ± 0.4 pc) |
| Absolute magnitude (MV) | –0.90 |
| Details | |
| Mass | 1.5 M☉ |
| Radius | 59 R☉ |
| Surface gravity (log g) | 1.4 cgs |
| Temperature | 3,679 K |
| Metallicity [Fe/H] | 0.32 dex |
| Rotational velocity (v sin i) | 7.0 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
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