The near-Earth asteroid Kamo’oalewa, according to a team of experts led by the University of Arizona, could be a small moon.
According to a new report published in Nature Communications Earth and Environment by a team of astronomers led by the University of Arizona, a near-Earth asteroid dubbed Kamo’oalewa could be a part of our moon.
Kamo’oalewa is a quasi-satellite, a type of near-Earth asteroid that orbits the sun yet stays close to the Earth. Because these objects are weak and difficult to view, nothing is known about them. The PanSTARRS telescope in Hawaii spotted Kamo’oalewa in 2016, and the name – which comes from a Hawaiian creation song – alludes to an offspring that journeys on its own. The asteroid is about the size of a Ferris wheel, with a diameter of 150 to 190 feet and a distance of about 9 million miles from Earth.
Kamo’oalewa can only be seen from Earth for a few weeks in April due to its orbit. Because of its modest size, it can only be observed using one of the world’s largest telescopes. A team of astronomers led by planetary sciences graduates student Ben Sharkey discovered that Kamo’oalewa’s pattern of reflected light, known as a spectrum, matches lunar rocks from NASA’s Apollo missions, implying it came from the moon, using the UArizona-managed Large Binocular Telescope on Mount Graham in southern Arizona.
The team can’t yet be sure how it may have broken loose. The reason, in part, is because there are no other known asteroids with lunar origins.
“I looked through every near-Earth asteroid spectrum we had access to, and nothing matched,”said Sharkey, the paper’s lead author.
Sharkey’s discussion with his adviser, UArizona associate professor Vishnu Reddy, about Kamo’oalewa’s origins, resulted in another three years of searching for a viable explanation.
“We doubted ourselves to death,” said Reddy, a co-author who started the project in 2016. After missing the chance to observe it in April 2020 due to a COVID-19 shutdown of the telescope, the team found the final piece of the puzzle in 2021.
“This spring, we got much needed follow-up observations and went, ‘Wow it is real,’” Sharkey said. “It’s easier to explain with the moon than other ideas.”
Another hint to Kamo’oalewa’s lunar origins is its orbit. It has a similar orbit to the Earth, albeit with a minor inclination. According to research co-author Renu Malhotra, a UArizona planetary sciences professor who lead the orbit analysis section of the study, its orbit is not typical of near-Earth asteroids.
In a dark sky, Kamo’oalewa is around 4 million times fainter than the faintest star visible to the naked eye.
“These challenging observations were enabled by the immense light gathering power, of the twin 8.4-meter telescopes of the Large Binocular Telescope,”said study co-author Al Conrad, a staff scientist with the telescope.
Reference: “Lunar-like silicate material forms the Earth quasi-satellite (469219) 2016 HO3 Kamoʻoalewa” 11 November 2021, Communications Earth & Environment.