Turns out the moon isn't the only object hanging around Earth.
Scientists discovered an asteroid named 2016 HO3 that sticks so close to Earth as it orbits the sun that astronomers have labeled it a "quasi-satellite."
"Our calculations indicate 2016 HO3 has been a stable quasi-satellite of Earth for almost a century, and it will continue to follow this pattern as Earth's companion for centuries to come," Paul Chodas, manager of NASA's Center for Near-Earth Object Studies, said in a statement.
Astronomers estimate the asteroid is between 130 feet and 330 feet wide. Earth's gravity keeps it chained to the planet: It never comes closer than 9 million miles, but never strays farther than 24 million miles.
Here's what its orbital path around Earth looks like. Earth is the blue dot and the asteroid is the yellow dot:
"In effect, this small asteroid is caught in a little dance with Earth," Chodas said.
We can't call it a second moon because it's too distant and it doesn't orbit Earth in the neat elliptical path the moon takes. It orbits far ahead of Earth half the time, and lags behind it the other half.
This isn't the first "quasi moon" of Earth that we've discovered. Back in 1986 scientists found an asteroid called 3753 Cruithne that's also referred to as a quasi-satellite of Earth. There are probably many others too.
The fact that we're not even aware of all the objects orbiting Earth, shows just how much more space exploration we have to do.