NASA identifies a new mini-moon orbiting Earth

As far as we know, it is not common for asteroids to enter Earth's gravitational field for very long.  Over 10 years ago, for instance, an asteroid called 2003 YN107 entered our vicinity, orbiting Earth, but then left shortly after.

Now scientists have revealed an asteroid that has likely been orbiting our planet for 100 years.  It is called asteroid 2016 HO3 and has an elliptical path around the planet, many times further away than the moon that we know and love.

“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 Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory. “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 believes that this current asteroid is "much more locked onto us" and will be with us for centuries to come.