A tiny mystery object is zipping past the Earth today, providing astronomers with an excellent opportunity to finally confirm it as being the upper stage of a Centaur rocket that was launched by NASA in 1966.
Is it or isn’t it? This is the question that astronomers have been asking since September, when scientists with the Pan-STARRS1 survey in Maui, Hawai’i, first spotted the object, named 2020 SO. Astronomers have good reason to believe it’s returning space junk, specifically a Surveyor 2 Centaur rocket booster dating back to the 1960s. Trouble is, they haven’t actually been able to prove it.
2020 SO normally orbits the Sun, but Earth’s gravity has, albeit temporarily, turned this object into an artificial minimoon. The object will complete a pair of orbits around our planet before it adopts a new orbit around the Sun, but today (December 1, 2020) is a special day, as the object is making its closest approach to Earth.
Gianluca Masi, an astronomer with the Virtual Telescope Project 2.0—a group that uses remotely controlled telescopes to observe space—took the opportunity to capture a photo of the object last night.
“I managed to get a tracked image of the object, but also a trail [upper left in the photo] and the latter shows a dotted pattern, basically a bright dot, followed by a fainter one and so on,” Masi explained in an email. “This suggests the object was rotating, with a period of about 10 seconds.”
Masi said he’ll have more to share soon, so we’re looking forward to that.
Looking at the image, we still can’t be sure that we’re gazing upon the lost rocket booster, but we so want to believe that it is. The purpose of NASA’s Surveyor 2 mission was to examine the lunar surface prior to the Apollo missions. Launched on September 20, 1966, the mission started well, but on the second day, a thruster on Surveyor 2 failed to ignite, throwing the spacecraft into a spin. Surveyor 2 crashed onto the lunar surface, while the Centaur upper stage drifted past the Moon and into an unknown orbit around the Sun.
After that, no one gave it much thought.
NASA’s Surveyor program was actually quite successful, despite two failures out of seven attempts to perform soft landings on the lunar surface between 1966 and 1968. You can learn more about these missions here.
Soon after 2020 SO was spotted by PanSTARRs, astronomers at the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory flagged the object on account of its unexpected behavior. The object’s orbit was more Earth-like than asteroid-like, featuring a nearly circular orbit within Earth’s orbital plane. That’s not typically seen in asteroids.
Additional observations showed that