Delta Ophiuchi

Delta Ophiuchi (δ Oph, δ Ophiuchi) is a star in the constellation Ophiuchus. It has the traditional name Yed Prior. The star Epsilon Ophiuchi, with which it forms a naked eye optical double, is 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 around 171 light-years (52 parsecs) from Earth.