What qualifies a space rock to be called a moon? Most would define a “moon” as a satellite that orbits a planet but, if you think outside the circle and include celestial bodies that spend a lot of time in the vicinity of a planet, then 2014 OL339, a newly discovered asteroid, is the Earth’s newest moon.
Asteroid 2014 OL339 was discovered on July 29 by astronomer Farid Char of the Chilean University of Antofagasta. It’s 150 meters (490 feet) wide and has been traveling with the Earth for at least 775 years. However, it’s not in orbit around our planet. 2014 OL339 is in what astronomers call a “resonant orbit,” meaning it is circling the Sun in an orbit close enough to Earth’s that they exert gravitational forces on each other.
2014 OL339 is in an elliptical orbit and takes 364.92 days to travel around the sun. The gravitational pull of the Earth gives it an eccentric wobble which causes it to look like it’s circling backward in relation to the stars. Because of that, the orbit is slowly destabilizing and the partnership with Earth will probably end in around 165 years, giving them a 1,000 year relationship.
Astronomers refer to these celestial traveling companions as quasi-satellites and Earth has a total of four so far, with 2014 OL339 joining 2004 GU9, 2006 FV35 and 2013 LX28. Jupiter leads the solar system with six documented quasi-satellites, although it probably has more yet to be discovered.
Should we get excited about the discovery of 2014 OL339? It doesn’t hit your eye like a big pizza pie since it’s not visible to the naked eye at all. It’s not really in orbit around Earth and is not even planning to stick around. Unless my dog starts howling at it or a werewolf shows up the next time it’s in a full quasi-satellite phase, 2014 OL339 is no moon to me.