“Asteroid” 2020 SO

UPDATE: During yesterday’s (01 December) close pass scientists used NASA’s Infrared Telescope Facility (NIRTF) on top of Mauna Kea to compare 2020 SO’s IR signature with that of a Centaur upper stage currently in Earth orbit. They matched, leading the scientists to state that 2020 SO is indeed the Centaur upper stage that sent Surveyor 2 towards the Moon in 1966.

I was finally able to image MPC object 2020 SO last night. The object was discovered on the 17th of September by the Pan-STARRS 1 telescope and given the designation 2020 SO. This animation is a series of 300 second images and you can see by the amount the object streaked, how fast it is moving. That apparent movement is due to its proximity. The object is currently trapped by Earth’s gravity and will remain in orbit for several months until the Earth and Moon’s gravity combine to send it back into its own heliocentric orbit.

What is unique about 2020 SO is its orbit and speed prior to its encounter with Earth is very unusual for an asteroid. It is not unusual for a manmade object launched from Earth. 2020 SO is suspected to be the Centaur upper stage that sent the 1966 Surveyor 2 probe towards its rendezvous with the Moon. The probe impacted the Moon but the Centaur continued, as expected, into an solar orbit. The Centaur was first successfully flown in 1963 and has been upgraded several times.

Atlas V version of the Centaur upper stage. Credit: NASA (2005)

I am guessing here but I think the late, great Arecibo radio telescope would have been tasked with observing the object during its close December pass. Spectroscopic studies will be carried out with the intent on identifying the object as the Centaur based on its titanium-oxide white paint.