Mystery Object Could Be Second 'Minimoon' Ever Detected Around Earth, Astronomers Say

Astronomers have spotted a small, mysterious object orbiting the Earth which could be the second "minimoon" detected in orbit around our planet.

The object, which has been designated the provisional name 2020 CD3 by the International Astronomical Union's Minor Planet Center, was first observed on February 15 by astronomers Kacper Wierzchos and Teddy Pruyne at the Catalina Sky Survey—which operates from the University of Arizona's Lunar and Planetary Laboratory in Tucson.

Since then, a team at the international Gemini Observatory have managed to capture a fascinating full color image of the object.

At present, it is not clear whether 2020 CD3 is natural in origin—a small space rock known as a "minimoon," for example—or man-made technology, such as a satellite or other piece of space debris.

If the former hypothesis is correct, the discovery would be particularly significant given that only one natural satellite other than the moon has previously been detected around the Earth.

This object, dubbed 2006 RH120, is a nearly 10-foot wide asteroid which normally orbits the sun but was temporarily captured by the Earth's gravitational pull in 2006, before being shot out into space again.

"Either way [2020 CD3] is a very compelling object and needs more data to determine what it is," Grigori Fedorets, lead astronomer of the Gemini observations from Queen's University Belfast in the U.K., said in a statement.

"If it will be indeed of natural origin, it would be the second temporary moon discovered in space, establishing a population," Fedorets told Newsweek. "It will provide more knowledge about the composition of the smallest asteroids in the solar system—of which not much is known—linking in to the overall fundamental question of the formation of the solar system."

The Gemini image—captured by the Gemini North telescope located at the summit of Maunakea in Hawaii on February 24—shows 2020 CD3 as a tiny spot of light amidst the light trails of several stars. The image was created by combining three different images that were snapped with different color filters.

"The stars are trailing because this object is moving relative to the background stars and the 8-meter Gemini North telescope was tracking on this object," Fedorets said.

Capturing images of fast-moving, small objects like this with large telescopes similar in size to Gemini is a challenge.

"Obtaining the images was a scramble for the Gemini team because the object is quickly becoming fainter as it moves away from Earth. It is expected to be ejected from Earth's orbit altogether in April," John Blakeslee, Head of Science at the international Gemini Observatory, said in a statement.

2020 CD3
An image of 2020 CD3 (center) captured by the 8-meter Gemini North telescope. The international Gemini Observatory/NSF’s National Optical-Infrared Astronomy Research Laboratory/AURA

According to Fedorets, astronomers are now trying to learn more about the object to determine what it is and where it might have come from. For example, determining the the reflectivity of 2020 CD3 can help scientists to decipher whether it is man-made or natural in origin, given that man-made objects, such as space rocket debris, tend to more reflective than pieces of rock for example.

While only one minimoon—tiny asteroids measuring up to around 80 inches in diameter—has ever been confirmed around the Earth, scientists think there may actually be thousands of these objects in orbit around our planet at any one time, according to a study published in the journal Frontiers in Astronomy and Space.

These may often go undetected by traditional asteroid surveys because they are so small, faint and fast-moving. Nevertheless, upcoming observatories—such as the Vera C. Rubin Observatory—may be able to detect further minimoons

We expect to find a population of these objects once the Rubin Observatory is operational," Fedorets said. "Stay tuned!"

This article was updated to include additional comments from Grigori Fedorets.