Earth Has a Second Moon—For Another 300 Years, At Least

There’s another sorta, kinda moon in a sorta, kinda orbit around Earth that was discovered only in 2016. The quasi-moon - named Kamo’oalewa, after a Hawaiian word that refers to a moving celestial object - is not much to speak of, measuring less than 50 m (164 ft) across.

It circles the Earth in a repeating corkscrew-like trajectory that brings it no closer than 40 to 100 times the 384,000 km (239,000 mi.) distance of our more familiar moon. Its odd flight path is caused by the competing gravitational pulls of the Earth and the sun, which continually bend and torque the moonlet’s motions.

And according to a new study in Nature, we may at last know how it was formed.

The moon’s been getting bombarded by space rocks for billions of years, resulting in all manner of lunar debris getting ejected into space (nearly 500 bits of which have made it to the surface of the Earth as meteorites). Kamo’oalewa is one such piece of lunar rubble that spiraled away from the moon.

But rather than landing on Earth or simply tumbling off into the void, it found itself a quasi-satellite in its own right.