Zeta Ophiuchi — Star in Ophiuchus

Zeta Ophiuchi is a hot blue main-sequence star of spectral type O9.5V at magnitude 2.56, one of the few O-type stars visible to the naked eye. Located roughly 460 light-years from Earth, it has a surface temperature of about 34,000 K and a luminosity around 90,000 times solar. Zeta Oph is a famous runaway star — it is hurtling through space at about 30 km/s, likely ejected when its companion star exploded as a supernova.

Located in the southern part of Ophiuchus, near the border with Scorpius. It appears as a bright blue-white star in a relatively sparse region of sky. The infrared bow shock it creates as it plows through interstellar gas is a famous Spitzer Space Telescope image but is not visible in amateur instruments. Best observed from June through September.

Zeta Ophiuchi has no traditional proper name. Its runaway nature was discovered in the mid-20th century when proper motion studies showed it moving at an abnormally high velocity. Tracing its path backward in time points to the Scorpius-Centaurus OB association, confirming it was ejected from a binary system about 1–2 million years ago.