Near-Earth Asteroid Kamo`oalewa Might Be An Ancient Fragment Of The Moon

Researchers from the University of Arizona published a new study suggesting a near-Earth asteroid called Kamo`oalewa might be a moon fragment. The asteroid is a quasi-satellite, which is a group of near-Earth asteroids that orbit the sun close to Earth. Researchers know very little about this class of objects overall because they are very faint and hard to observe.

Astronomers utilizing the PanSTAARS telescope in 2016 discovered Kamo`oalewa and chose its name. The name comes from a Hawaiian creation chant and suggests offspring that travels alone. Kamo`oalewa isn't a particularly large asteroid between 150 and 190 feet in diameter. At the closest point in its orbit, it's about 9 million miles away from our planet.

The orbital path Kamo`oalewa takes around the sun prevents it from being observed anytime other than for a few weeks every April. The small stature of the asteroid makes it unobservable by most telescopes. Astronomers from the University of Arizona utilized the Large Binocular Telescope located on Mount Graham in Arizona. Using data gathered from the telescope, astronomers discovered that the pattern of reflected light, called spectrum, that emanates from Kamo`oalewa matches lunar rocks recovered during the Apollo era.

This finding suggests the asteroid is actually a fragment of the moon. For now, exactly how the moon fragment may have separated is unknown. Currently, there are no other known asteroids that came from the moon. During the project, the researchers investigated every other near-earth asteroid spectrum available and found no other matches.

In April 2021, the researchers conducted follow-up observations after the telescope had been closed during April 2020 due to the pandemic. The team found that the orbit the asteroid takes is another clue that it originated from the moon. Its orbit is very similar to the orbit of the earth but does have a notable tilt. Its orbit is also different from those of other near-Earth asteroids.

Study co-author Renu Malhotra says it's unlikely that a standard near-earth asteroid would move on its own into a quasi-satellite orbit similar to that of Kamo`oalewa. Another interesting tidbit from the scientists is that the asteroid won't remain in its current orbit for long. Estimates peg Kamo`oalewa as having entered the orbit it's in now about 500 years ago and only remaining in the orbit for about another 300 years.

The faintness of the asteroid contributes to the difficulty in determining its origins for sure. Kamo`oalewa is 4 million times fainter than the faintest star the human eye can see. The incredible light-gathering power of the twin 8.4-meter telescopes that make up the Large Binocular Telescope enabled the astronomers to discover such a small and dim object.

Gathering data on this particular asteroid is slow due to it only being visible a few weeks each year. Scientists will undoubtedly perform follow-up observations to learn more about the asteroid. For now, the researchers offered no hypothesis on how the asteroid might've been created. For their study, researchers also use data from the Lowell Discovery Telescope in Arizona. Study authors include Olga Kuhn, Christian Veillet, Barry Rothberg, and David Thompson from the Large Binocular Telescope; Audrey Thirouin from Lowell Observatory and Juan Sanchez from the Planetary Science Institute.