Earth Might Have A New Mini-Moon. At Least For A Short While.

The orbit of 2020 CD3 around the Earth. The white band is the orbit of the Moon. Tony Dunn via Wikimedia Common

The neighborhood of our planet is a very busy place full of space rocks, big and small, most of which we are not aware of. But once in a while, they come close enough to be ensnared by our planet. Some burn in the atmosphere, some hit the surface, and some end up being captured in orbits around the Earth. At least for a while. This might be the case for the newly discovered 2020 CD3.

Astronomers Kacper Wierzchos and Theodore Pruyne spotted the object on February 15 as part of observations for the Catalina Sky Survey performed at Mount Lemmon Observatory. The object is most likely of natural origin (not discarded space junk) and is between 1.9 and 3.5 meters (6.2 and 11.5 feet) in length, assuming it has the same composition as carbonaceous asteroids, the most common type in the Solar System.


The International Astronomical Union Minor Planet Center has shared an electronic circular discussing the recent observations, asking more astronomers to get involved in observing what they describe as a temporarily captured object.

Physics teacher Tony Dunn used the Orbit Simulator to reconstruct the object's movements over the last three years based on the observations from the last few days, revealing just how incredibly complex the interaction between the Earth-Moon System can be on the minor objects in the Solar System.


The potential mini-moon jumped up and down the orbital plane, moving millions of kilometers away from Earth before coming back to just thousands of kilometers away. But based on what we know so far, our planet's relationship with this new companion is not built to last. The simulator suggests that it will leave Earth orbit in April 2020.

If further astrometric measurements hold up, 2020 CD3 will be the second confirmed mini-moon after 2006 RH120 , which was also discovered by the Catalina Sky Survey. That object, which was roughly the same size, orbited the Earth between September 2006 and June 2007.


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