The faint glow of a near-Earth asteroid mysteriously shimmers on astronomers’ telescopes every April for a few weeks. Observing the annual event with a group of astronomers, an unexpected discovery regarding the little shard was made: it doesn’t appear to be any old space rock. It appears to be a shattered chunk of the moon. The Hawaiian name for the Ferris wheel-sized chip is Kamo’oalewa, and proof supporting its lunar identity was published in the journal Nature Communications Earth & Environment on Thursday.
Instead, Sharkey and his colleagues discovered that the rock had a reflected light pattern, or spectrum, that was strikingly similar to moon rocks returned by NASA’s Apollo missions. However, this isn’t the only evidence of Kamo’oalewa’s lunar roots. The quasi-satellite, a type of near asteroid that orbits both the sun and the Earth, orbits our planet with an odd tilt, which is why it only appears once a year in the night sky. It’s quite unlikely that a common near-Earth asteroid would travel into a quasi-satellite orbit like Kamo’oalewa’s on its own. The enormous light gathering power of the Large Binocular Telescope’s twin 8.4-meter (27.5-foot) telescopes enabled these difficult investigations.
The project began in 2016 and lasted a few years, but due to COVID-19 constraints, the team missed the asteroid’s arrival window in 2020. Now, in 2021, they’re confident enough in the amount of data they’ve gathered to reveal Kamo’oalewa’s unique past. “This spring, we got much-needed follow-up observations and went, “Wow, it’s real,” said Sharkey. The moon is easier to explain than other concepts. Only one thing remains unanswered: how did Kamo’oalewa break away from the moon? Because this is the first near-Earth asteroid to show lunar characteristics, it’s unclear whether the space rock is a one-off or if there are other moon fragments lying in the solar system waiting to be discovered.