Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii has discovered Earth's new quasi-satellite. Designated as 2016 HO3, this newly discovered near-Earth object has been our planet's constant companion for almost a century.
The asteroid is too distant to be considered a true satellite of our planet, but it is the best and most stable example to date of a near-Earth companion, or "quasi-satellite."
"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.
We know for one other asteroid - 2003 YN107 - that 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," said Chodas.
Asteroid 2016 HO3 - orbital diagram - June 16, 2016. Credit: NASA/JPL NEO
In its yearly trek around the sun, asteroid 2016 HO3 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. Its orbit is also tilted a little, causing it to bob up and then down once each year through Earth's orbital plane. In effect, this small asteroid is caught in a game of leap frog with Earth that will last for hundreds of years, NASA reported.
The asteroid's orbit also undergoes a slow, back-and-forth twist over multiple decades.
"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. 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," Chodas added.
Asteroid 2016 HO3 was first spotted on April 27, 2016. Its size has not yet been firmly established, but it is likely larger than 40 meters (120 feet) and smaller than 100 meters (300 feet). It never comes closer than 14 million km (9 million miles) from Earth.
Featured image: Asteroid 2016 HO3 - orbital diagram - June 16, 2016. Credit: NASA/JPL NEO