New 'mini-moon' orbiting Earth — for now, astronomers say

A visiting mini-moon is circling Earth, according to astronomers who discovered the cosmic squatter in our planet's orbit.

The tiny asteroid, dubbed 2020 CD3, was spotted by astronomers in Tucson, Arizona, on Feb. 15.

"BIG NEWS," Kacper Wierzchos, a researcher with the Catalina Sky Survey at the University of Arizona's Lunar and Planetary Lab, tweeted Tuesday. "Earth has a new temporarily captured object/Possible mini-moon called 2020 CD3. On the night of Feb. 15, my Catalina Sky Survey teammate Teddy Pruyne and I found a 20th magnitude object."

Wierzchos said that the object measures about 6 feet to 11 feet across and that its orbit suggests that it entered Earth's orbit around three years ago.

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He added that the discovery is a "big deal" because, out of roughly 1 million known space rocks, this is "just the second asteroid known to orbit Earth (after 2006 RH120, which was also discovered by the Catalina Sky Survey)."

The cosmic interloper was officially cataloged by the International Astronomical Union's Minor Planet Center on Tuesday. The center, founded in 1947, collects observational data on asteroids, comets and natural satellites in the solar system.

In its official designation, the IAU said observations "indicate that this object is temporarily bound to Earth." The organization added: "No evidence of perturbations due to solar radiation pressure is seen, and no link to a known artificial object has been found. Further observations and dynamical studies are strongly encouraged."

The last asteroid to get caught in Earth's orbit was 2006 RH120. The space rock, which orbits the sun and passes close to Earth every few decades, was captured by the planet's gravity in June 2006 and stayed until around September 2007, before it swung back out into the solar system.

More information about the mini-moon could be revealed in the coming weeks and months as astronomers continue to observe it.

The Catalina Sky Survey, a NASA-funded project, aims to scan the cosmos to discover and track near-Earth objects, particularly those that could pose a threat to Earth.