Off the asteroid list: Mystery object orbiting Earth is 54-year-old rocket

An Atlas Centaur 7 rocket on the launchpad at Cape Canaveral, Fla., in 1966
An Atlas Centaur 7 rocket on the launchpad at Cape Canaveral, Fla., in September 1966.
(Convair/San Diego Air and Space Museum)

A mysterious object temporarily orbiting Earth is a 54-year-old rocket and not an asteroid after all, astronomers confirmed Wednesday.

Observations by a telescope in Hawaii clinched its identity, according to NASA’s Jet Propulsion Laboratory.

The object was classified as an asteroid after its discovery in September. But NASA’s top asteroid expert, Paul Chodas, quickly suspected that it was the Centaur upper rocket stage from Surveyor 2, a failed 1966 moon-landing mission. Size estimates had put it in the range of the old Centaur, which was about 32 feet long and 10 feet in diameter.


Chodas was proven right after a team led by the University of Arizona’s Vishnu Reddy used an infrared telescope in Hawaii to observe not only the mystery object but also a Centaur from 1971 still orbiting Earth. The data from the images matched.

“Today’s news was super gratifying!” Chodas said via email. “It was teamwork that wrapped up this puzzle.”

The object formally known as 2020 SO entered a wide, lopsided orbit around Earth last month and made its closest approach Tuesday at slightly more than 31,000 miles from Earth. It will depart the neighborhood in March, shooting back into its own orbit around the sun.

Its next return is expected in 2036.