In a new paper published in the Astronomical Journal, astronomers from the United States, Canada and Europe provide a detailed characterization of the physical properties and orbital evolution of the asteroid 2020 CD3 — Earth’s second discovered temporary natural satellite, or minimoon.

Until 2020, only one minimoon had been discovered — 2006 RH120, a tiny near-Earth asteroid with a diameter of approximately 2-3 m (6.6-9.8 feet).

The second known minimoon, 2020 CD3, was discovered on February 15, 2020 by the Catalina Sky Survey 1.5-m telescope on Mt.

Discovering an object on a geocentric orbit always raises suspicion of an artificial origin, but during the 2.5 weeks following its discovery 2020 CD3 could not be linked to any known artificial object nor could a natural origin be ruled out.

“The discovery in February was significant as the only other minimoon astronomers have documented was recorded back in 2006, spending around a year on an orbit around the Earth,” said Dr.

Fedorets and colleagues obtained high-precision astrometric follow-up observations in February-May 2020 with the Lowell Discovery Telescope (LDT) and several other ground-based observatories.

This distinguishes it from another recently-discovered minimoon, 2020 SO, which astronomers believe may be the Centaur upper stage rocket booster that helped lift NASA’s Surveyor 2 spacecraft toward the Moon in 1966.

Establishing Earth’s Minimoon Population through Characterization of Asteroid 2020 CD3