Small Asteroid 2016 HO3 is a Quasi-Satellite of Earth

Posted on June 17, 2016

2016 HO3 orbit diagram

2016 HO3 is a recently discovered small asteroid that orbits the Earth and the sun. It was first spotted on April 27, 2016 by the Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii. NASA calls the asteroid a near-Earth companion or quasi-satellite of Earth. It is too far away to be considered a true Earth satellite. A larger version of the orbit diagram can be found here.

Paul Chodas, manager of NASA's Center for Near-Earth Object (NEO) Studies, says in a statement, "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."

2016 HO3 spends about half its time closer to the sun than the Earth as it makes its annual journey around the sun. It has an orbit that is slightly tilted. NASA says it also undergoes a "slow, back-and-forth twist" over multiple decades.

Chodas says, "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."

Take a look:



Image: NASA/JPL-Caltech