Earth has captured a tiny object from its orbit around the Sun and will keep it as a temporary satellite for a few months before it escapes back to a solar orbit. But the object is likely not an asteroid; it’s probably the Centaur upper stage rocket booster that helped lift NASA’s ill-fated Surveyor 2 spacecraft toward the Moon in 1966.
This story of celestial catch-and-release begins with the detection of an unknown object by the NASA-funded Pan-STARRS1 survey telescope on Maui in September. Astronomers at Pan-STARRS noticed that this object followed a slight but distinctly curved path in the sky, which is a sign of its proximity to Earth. The apparent curvature is caused by the rotation of the observer around Earth’s axis as our planet spins. Assumed to be an asteroid orbiting the Sun, the object was given a standard designation by the Minor Planet Center in Cambridge, Massachusetts: 2020 SO. But scientists at the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory in Southern California saw the object’s orbit and suspected it was not a normal asteroid.