Astronomers have just discovered that the dwarf planet Makemake has its own tiny dark moon. Until now, it was the only officially recognized dwarf planet without a moon. The little satellite nicknamed MK2 was found orbiting Makemake at the outer fringes of our solar system in the Kuiper Belt. The moon is just 100 miles wide while its parent dwarf planet is about 870 miles across.

Distant Dwarf Planet Makemake Has Its Own Dark Moon

MK2 couldn’t escape the Hubble’s eyes

The satellite MK2 evaded detection for over a decade, thanks to the glare of its icy parent planet. It was picked up in April 2015 when the Hubble Space Telescope spotted a faint point of light close to the dwarf planet. Hubble’s Wide Field Camera 3 is capable of discerning faint objects located close to the super bright ones. Alex Parker of the Southwest Research Institute said MK2 is 1,300 times fainter than the dwarf planet.

The discovery of MK2 will help astronomers determine whether the moon was formed out of collision or Makemake’s gravity snatched it. It will also offer insights about the dwarf planet itself, such as its mass and density. Discovered in 2005, Makemake is known to be covered in frozen methane and shaped like a flattened sphere. The dwarf planet orbits the sun once every 310 Earth years.

The dark patch is in Makemake’s orbit, not on its surface

Scientists will observe the moon further to find out the shape of its orbit and how many times it circles its host planet in a given period. It could also solve a huge mystery about the icy dwarf planet. Makemake is a continually bright dwarf planet, suggesting its surface is uniformly covered in reflective ices. But thermal measurements of the dwarf planet were slightly varied, indicating that there was at least one dark patch on its surface. The two data sets could never be reconciled because the dark patch never appeared in observations.

Parker said that dark material isn’t on the surface of Makemake. It is in the icy planet’s orbit. The dark moon may account for most of the heat signatures.