Apparently, our Moon isn’t the only satellite circling Earth. A “quasi-moon,” initially thought to be a piece of space junk, was found in a near-Earth orbit around the Sun last year. Upon further observation, researchers say Earth’s newly found companion is actually something less than 300 feet in diameter.
The “quasi-moon,” or “quasi-satellite,” as NASA terms it, was spotted on April 27, 2016, by the Pan-STARRS 1 asteroid survey telescope in Haleakala, Hawaii. It turns out it’s a small asteroid named 2016 HO3, according to NASA.
“Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the sun, we refer to it as a quasi-satellite of Earth,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California.
Asteroid 2016 HO3, possibly between 120 feet (40 meters) and 300 feet (100 meters) in diameter, has remained a constant companion for Earth, as they orbit the Sun together, and have been doing so for nearly a century.
“This new asteroid is much more locked onto us. Our calculations indicate 2016 HO3 has been a stable quasi-satellite of Earth for almost a century, and it will continue to follow this pattern as Earth’s companion for centuries to come,” Chodas explained.
The slightly tilted asteroid gets closer to the Sun than Earth, and moves ahead of our planet for half of the time each year. For the other half of the time, it moves farther out from Earth, thus falling behind.
“The asteroid’s loops around Earth drift a little ahead or behind from year to year, but when they drift too far forward or backward, Earth’s gravity is just strong enough to reverse the drift and hold onto the asteroid so that it never wanders farther away than about 100 times the distance of the moon,” explained Chodas.
“The same effect also prevents the asteroid from approaching much closer than about 38 times the distance of the moon. In effect, this small asteroid is caught in a little dance with Earth,” he added.
As asteroid 2016 HO3 never gets any closer than 9 million miles (14 million kilometers) from Earth, it is hard for researchers to study it.
“While HO3 is close to the Earth, its small size—possibly not larger than 100 feet—makes it challenging target to study, our observations show that HO3 rotates once every 28 minutes and is made of materials similar to asteroids,” said Vishnu Reddy, an assistant professor at the university, in a statement.
Reddy and his team also detected that the asteroid reflects light—just like the Moon—in addition to spinning on its axis for only two times every 60 minutes, National Geographic reported. Hence, this natural satellite has also been humorously dubbed Earth’s “second little moon,” though it’s a bit of a far cry from the real moon!