"Makemake is in the class of rare Pluto-like objects, so finding a companion is important," Southwest Research Institute's Alex Parker said. "The discovery of this moon has given us an opportunity to study Makemake in far greater detail than we ever would have been able to without the companion."

Astronomers plan to look more closely into the satellite to find out if it's the "warm region" they've been seeing on Makemake's surface, which is inconsistent with its icy shell. They also intend to observe its movements: a tight orbit means it's the product of a collision, while a wide one means it was captured from the Kuiper belt. Either way, MK 2 -- just like our Earth's own satellite -- has been orbiting Makemake for billions of years.