The fragment of the Moon that orbits the Earth

The asteroid is called Kamo’oalewa. It’s a quasi-satellite of the Earth. What does that mean? It orbits the Sun but stays relatively close to our planet. Its name is Hawaiian for a ‘son who travels alone’. It is about the size of a Ferris wheel, between 45 and 57 meters in diameter. And it’s about 14 million kilometers away from us. And apparently, it once belonged to the Moon. It’s the fragment of the Moon that orbits the Earth.

The fragment of the Moon orbiting the Earth is called Kamo'oalewa.
The fragment of the Moon orbiting the Earth is called Kamo’oalewa.

Hidden Object

Astronomers at the University of Arizona (USA) claim to know its origin. It would be a lost fragment of the Moon that could have been ejected by an ancient impact.

Kamo’oalewa is not an easy object to observe. It is about 4 million times fainter than the faintest star we can see.

It was discovered by the PanSTARRS telescope in Hawaii in 2016. Because of its orbit, it can only be observed for a few weeks each April. It is only seen using one of the largest telescopes on Earth: the Large Binocular Telescope on Mount Graham in southern Arizona.

The spectrum of Kamo’oalewa matches that of moon rocks from NASA’s Apollo missions. This suggests it originated on the Moon.

It is not yet known how this rock could have broken off from the Moon. The reason, in part, is because there are no other known asteroids of lunar origin. “I looked through all the near-Earth asteroid spectra. Nothing matched,” says Ben Sharkey. He is lead author of the paper published in ‘Nature Communications Earth & Environment’.

Its orbit makes it a quasi-satellite.
Its orbit makes it a quasi-satellite.

Son of the Moon

For years, researchers debated Kamo’oalewa’s origins. “We doubted to death,” acknowledges Vishnu Reddy, co-author of the study. The team found the final piece of the puzzle in 2021.

“This spring, we got much-needed follow-up observations. And we said, ‘Wow, it’s real,'” Sharkey says. “It’s easier to explain with the moon than with other ideas.”

The orbit of the fragment of the Moon orbiting Earth is another clue to its lunar origins. It is similar to that of the Earth, but with the slightest tilt. Nor is it typical of nearby asteroids. “It won’t stay in this particular orbit for very long. Only about 300 years in the future. We estimate that it reached this orbit about 500 years ago,” says Renu Malhotra. She is a professor of planetary science at Arizona and also a co-author of the study.

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