It turns out Makemake -- an atmosphere-less dwarf planet in the outermost reaches of our solar system -- has been hiding a companion.
There, circling some 13,000 miles from the icy planetoid, scientists spotted a small moon, nicknamed MK2.
Alex Parker, a planetary astronomer at the Southwest Research Institute in Boulder, Colorado, told National Geographic that when he glimpsed the object during an analysis of Hubble observations back in April 2015, he assumed it wasn't the first time someone had spied the moonlet.
Instead, Parker quickly learned he'd discovered a moon 1,300 times fainter than its host dwarf planet.
As Hubble notes in its announcement, several previous visual sweeps of MK2 showed a lonely mass, one of several dwarf planets located in the Kuiper Belt -- a region of icy bodies beyond Neptune's orbit. The team of scientists ultimately observed MK2 thanks to Hubble's "unique ability to see faint objects near bright ones," it said.
"It is a very exciting discovery!" Parker, who led the image analysis for the observations, told The Associated Press. "It means that Makemake is no longer the odd-one-out in the moon-hosting Kuiper Belt dwarf planet club."
Makemake, named after the god of fertility in the Rapa Nui mythology of Easter Island, is 870 miles wide and takes roughly 310 Earth-years to circle the sun. In comparison, the newly discovered moon has a diameter of about 100 miles.
Parker said in a statement that the discovery will provide researchers "an opportunity to study Makemake in far greater detail," perhaps answering questions about the mass, origin and evolution of the dwarf-planet system.