Earth has an entourage: a handful of small quasi-satellites that hang around in unstable orbits as the planet circles the sun. Now, new evidence from Arizona telescopes suggests one of them is made of material from the moon.

The research appears in the journal Communications Earth & Environment. 

Roughly one-third the size of an American football field, Kamo'oalewa is only observable for about a month each year.

Data from the Large Binocular Telescope at Mount Graham and the infrared Lowell Discovery Telescope near Happy Jack surprised lead author Benjamin Sharkey of University of Arizona.

"Our reaction to it was to say, 'Alright, let's get more data.' And then in 2021, we got more data. And then we said, 'Well, okay, I think now we can say something about this,'" Sharkey said. 

He says they tried every other practical explanation, including a captured asteroid.

"At the end, we conclude that lunar material provides a better match than anything else we could come up with," he said. 

That, combined with its orbital path, suggests Kamo'oalewa might have broken off from the moon during an impact.

Addy Graham/University of Arizona.

An artist's conception of the quasi-satellite Kamo'oalewa.