A tiny asteroid orbiting Earth like a “semi-satellite” could be a missing part of the moon. Called Kamo`oalewa, a term in the Hawaiian anthem referring to wobbly celestial bodies, it is 40 meters in diameter and may have separated from the Moon after our satellite’s violent collision with an asteroid. The discovery, published in the journal Nature Communications Earth and Environment, is due to research conducted by the University of Arizona.
Discovered in 2016 thanks to the Pan-STARRS observatory in Hawaii, this asteroid is the smallest, closest and most distant celestial body orbiting our planet and the sun at the same time.
Due to its orbit, Kamo`oalewa can be observed from Earth only in April and with great difficulty, since its luminosity is 4 million times fainter than the luminosity of the faintest star that the human eye can see in a dark sky. To study it, the researchers then sent one of the world’s most powerful telescopes, the Large Binocular Telescope (Lbt) in Arizona to which Italy contributed significantly with the National Institute of Astrophysics (Inaf).
Thanks to this instrument, it was possible to observe the spectrum of light reflected from the surface of the asteroid, and based on the data collected, it was found that the composition of Kamo`oalewa is incredibly similar to the composition of lunar rock samples brought back to Earth by missions. To confirm this, the researchers analyzed the object’s orbit to reconstruct its evolution: all data indicate that Kamo`oalewa may have formed about 500 years ago and is the most realistic hypothesis, but the moment is impossible to verify, and ‘this was created by an asteroid impact on the Moon.
In 2019, the Chinese space agency CNSA announced the start of a robotic mission with the goal of reaching Kamo`alewa in 2024 and taking a sample to return it to Earth. The expedition called ZhengHe must continue toward another, more ambitious goal: to collect a portion of a comet.
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