Delta Ophiuchi
 Location of δ Ophiuchi (circled) |
|
| 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 | |
| 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 ± 0.16mas |
| 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 | |
Delta Ophiuchi (δ Ophiuchi, abbreviated Delta Oph, δ Oph), also named Yed Prior, 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)).
δ Ophiuchi (Latinised to Delta Ophiuchi) is the star's Bayer designation.
It bore the traditional name Yed Prior. Yed derives from the Arabic Yad meaning "the hand". Delta and Epsilon Ophiuchi comprise the left hand of Ophiuchus (the Serpent Bearer) that holds the head of the serpent (Serpens Caput). Delta is Yed Prior as it leads Epsilon across the sky. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Yed Prior for this star on 5 October 2016 and it is now so entered in the IAU Catalog of Star Names.
Delta Ophiuchi was a member of the indigenous Arabic asterism al-Nasaq al-Yamānī, the "Southern Line" of al-Nasaqān the "Two Lines", along with Alpha Serpentis, Delta Serpentis, Epsilon Serpentis, Epsilon Ophiuchi, Zeta Ophiuchi and Gamma Ophiuchi.
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