The Truth About Earth's New Mini Moon
The old moon that we've all come to know and love has a new neighbor temporarily snared by Earth's gravity. According to CNET, our new celestial visitor is a type of space rock from a category known as Near-Earth Objects (NEOs). NEOs include comets and asteroids whose known paths intersect with Earth's orbit. Many of these objects never come particularly near to the Earth, and only very small NEOs pose any threat of actually striking the planet, but occasionally one errant space rock gets caught in Earth's gravity and begins to orbit the planet, technically becoming a moon.
The NASA-funded Catalina Sky Survey is credited for spotting the new orbiter during routine NEO observations on February 15th. Kacper Wierzchos of the Catalina Sky Survey tweeted the announcement, "Earth has a new temporarily captured object/Possible mini-moon called 2020 CD3."
Mini-moon only a temporary visitor, but it's already been here for 3 years
Wierzchos' team believes that 2020 CD3 is a carbonaceous asteroid, a common type of near earth rock. It likely ranges in size from 1.9 to 3.5 meters in diameter — so about the size of a car. According to their calculations, The NEO probably entered its current orbit around the Earth about three years ago and has been lurking there ever since, undetected. That should give us all a bit of pause, since it's literally the job of projects like the Catalina Sky Survey to keep tabs on car-sized objects that might pose a risk of striking Earth.
This kind of thing has happened before. The last asteroid to enter Earth's orbit and become a temporary moon was 2006 RH120. Science writer Corey Powell noted that that rock cozied up to the Earth-moon system in 2006 and remained in orbit around the planet for 18 months.
If 2020 CD3 were planning to hang around in this neck of the solar system much longer, we'd probably have to find a better name. Unfortunately, the OG moon's new neighbor won't likely remain in its current orbit. According to Space.com, 2020 CD3 is caught in a "gravitational tug-of-war" between the Earth and the moon. As a result, it will likely be pulled out of orbit by the moon's influence and shot beyond the observable range. Oh, mini-moon, we hardly knew ye.