Introducing Earth's New Orbit Buddy: a Really Big Rock

Astronomers have noticed that Earth has had a travel buddy for the last few centuries, and that friend will be sticking around for some time as a "quasi-satellite of Earth."

A new study, conducted by Carlos and Raul de la Fuente Marcos of Complutense University of Madrid (UM) in Spain, details how the newly discovered asteroid called 2014 OL339 has actually been hanging out with our blue planet for the last 775 years, following the same orbital path around the Sun.

The asteroid, which is between 90 and 200 meters (295-656 feet) in diameter, is one of several nearby large space rocks that could compete for the honorary name of "moon" beside our own. However, while the giant cratered satellite that lights up our night sky orbits the Earth, these "quasi-satellites" are actually caught in the gravitational pull of the Sun. They just happen to be orbiting it at the same speed and level as we are.

2014 OL339 has been found to be particularly buddy-buddy with Earth, orbiting the Sun so close to the blue planet that it is affected by the Earth's gravitational pull, causing it to wobble. This wobble almost appears as if the asteroid is swinging back and forth behind the Earth, which was an admittedly difficult pattern to understand for astrophysicists.

According to the UM researchers, most planets and even some of this galaxy's larger asteroids can be seen accompanied by buddies like OL339. Jupiter, for instance, with its significant size and gravitational pull, has six quasi-satellites. Earth then only takes second place for largest entourage in our solar system. With the addition of 2014 OL339, it is now known to have four identified quasi-satellites.

But Earth's buddies won't be around forever. According to the researchers, 2014 OL339 will likely wobble right out of orbit in an estimated 165 years from now, showing that the Moon is still Earth's most reliable friend.

A study of 2014 OL339 was recently made public in an arXiv online release (PDF).