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Earth has a new(ish) quasi-moon

posted by Tim Carmody   Jun 17, 2016

About a hundred years ago, a tiny asteroid making its way around the sun got caught in Earth’s gravity well. Now it’s locked in an irregular orbit far around our planet, between 38 and 100 times the distance between the Earth and its proper moon.

quasi-moon.JPG

As it orbits the sun, asteroid 2016 HO3 spends about half of the time closer to the sun than Earth, and passes ahead of our planet. The other half of the time it falls behind.

It’s also in a tilted orbit, which causes it to weave up and down on the orbital plane like a bob on choppy waters. As NASA’s Paul Chodas put it in a press statement, “In effect, this small asteroid is caught in a little dance with Earth.”

In another couple of centuries, the asteroid will probably get far enough away that it’ll leave Earth behind forever. I wonder how many times this has happened — how many times the asteroids have been bigger, closer, but still not big or close enough to stay.