NASA spots a strange new asteroid playing "leap frog" with Earth

Updated by Brad Plumer

Heyyyyyy there, buddy. 

Earth has a new buddy. NASA astronomers have detected an asteroid that is constantly circling the Earth as part of its orbit around the sun. This "quasi-satellite," known as 2016 HO3, has been with us for nearly a century — and will probably stay with us for centuries to come.

The video below, from NASA's Center for Near-Earth Object Studies, shows 2016 HO3’s very odd trajectory:

Like many objects in the solar system, 2016 HO3 orbits the sun. But almost a century ago, it wandered close enough to us that it’s now constantly getting tugged by Earth’s gravity, forcing it to make loops around our planet.

As NASA explains:

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.

We don't have to worry about this asteroid crashing into us — 2016 HO3 never gets closer than about 38 times the distance of the moon and never gets further away than about 100 times the distance of the moon. (It’s still unclear how big the object is, but NASA estimates between 40 and 100 meters.)

Because it’s so far away, the asteroid isn’t technically considered a satellite of Earth. "We refer to it as a quasi-satellite of Earth," said Paul Chodas, manager of NASA's Center for Near-Earth Object (NEO) Studies, in a statement. "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."

This asteroid isn’t a threat to Earth — but NASA is looking for others that might be