The object is part of the Arjuna asteroid belt.
Speaking to Space.com, Universidad Complutense de Madrid professor Carlos de la Fuente Marcos — one of the people who discovered the mini-moon — described Arjuna as “a secondary asteroid belt made of space rocks that follow orbits very similar to that of Earth at an average distance to the sun of about 93 million miles.”
He said that some objects in the belt can come close enough to Earth and at velocities low enough (roughly 2.8 million miles away and 2,200 miles per hour) to allow them to temporarily orbit Earth.
Other scientists even think that, based upon its past trajectory, the asteroid might be a piece of Earth’s moon that flew off after a previous impact.
