Astronomers have discovered a new “quasi” moon orbiting Earth.
2016 HO3, as the asteroid is called, is at least 40 meters across and could be larger, up to 100 meters, researchers say, but it’s too far from Earth to qualify as a true satellite or mini-moon.
"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.
"One other asteroid -- 2003 YN107 -- followed a similar orbital pattern for a while over 10 years ago, but it has since departed our vicinity. 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."
The asteroid, NASA says, “spends about half of the time closer to the sun than Earth and passes ahead of our planet, and about half of the time farther away, causing it to fall 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," said 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."
2016 HO3 was first observed in April by the Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii.
Here's a video about 2016 HO3: