The terrestrial asteroid is a fragment from the moon, scientists say Asteroids

Scientists have identified what appears to be a small part of the moon that follows the Earth’s orbit around the Sun.

The asteroid, called Kamo`oalewa, was discovered in 2016, but until now relatively little has been known about it. New observations suggest that it could be a fragment from the moon that was thrown into space by an ancient lunar collision.

Kamo`oalewa is one of the Earth’s quasi-satellites, a category of asteroids orbiting the Sun but remaining relatively close to the planet – in this case about 9 m miles away.

Despite being close in astronomical terms, the asteroid is about the size of a Ferris wheel and about 4m times fainter than the faintest star visible to the naked eye. Therefore, the Earth’s most powerful telescopes are needed to make observations.

Using the large binocular telescope on Mount Graham in southern Arizona, astronomers found the spectrum of reflected light from Kamo`oalewa closely matched moonstones from NASA’s Apollo missions, suggesting that it originated from the moon. They had originally compared the light to that reflected from other terrestrial asteroids, but drew a blank.

“I looked through every near-Earth asteroid spectrum we had access to and nothing matched,” said Ben Sharkey, a PhD student at the University of Arizona and the paper’s lead author.

After missing the chance to observe Kamo`oalewa in April 2020 due to a telescopic shutdown during the coronavirus pandemic, the team found the last piece of the 2021 puzzle.

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

The observations also showed that Kamo`oalewa is in an unusual orbit, an orbit that would be unlikely for objects orbiting the Earth from the asteroid belt between Mars and Jupiter.

The team is uncertain about how the moon piece came to drift in space, partly because there are no other known asteroids of lunar origin. But they narrowed the time frame for the violent event to have taken place between 100,000 and 500 years ago.

Prof Stephen Lowry, an astronomer at the University of Kent, said: “While not 100% crucial, the team has made a strong argument that Kamo`oalewa may in fact be a collision fragment from such a violent event. [as a lunar collision]. “

The results are published in the journal Nature Communications Earth and Environment.

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