A tiny charcoal-black moon orbiting the icy dwarf planet Makemake in the Kuiper Belt has been discovered by NASA’s Hubble Space Telescope. The moon is designated S/2015 (136472) 1 and can also be called MK 2, is about 161 kilometres wide and is located 20.9 kilometres from Makemake.

Earlier infrared data cannot separate Makemake from MK 2 due to a lack of resolution. But the Hubble’s Wide Field Camera 3 revealed that the moon has a warmer surface than previously thought.

The observations were actually made in April 2015 but it has only been announced today. Discovering a moon can also provide more insight about the dwarf planet system like supporting the theory that most dwarf planets have moons.


This Hubble image reveals the first moon ever discovered around the dwarf planet Makemake. The tiny satellite, located just above Makemake in this image, is barely visible because it is almost lost in the glare of the very bright dwarf planet. Hubble’s sharp-eyed WFC3 made the observation in April 2015. Credits: NASA, ESA, and A. Parker and M. Buie (SwRI)

“Makemake is in the class of rare Pluto-like objects, so finding a companion is important,” explains Southwest Research Institute’s Alex Parker, who led the analysis of the discovery. “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.”

He also added that “Our preliminary estimates show that the moon’s orbit seems to be edge-on, and that means that often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake.”

The scientists believe that MK 2 is too small to gravitationally hold onto the bright icy crust of Makemake, the second brightest icy dwarf planet behind Pluto. This could explain the dark satellite’s colour which is similar to comets and other Kuiper Belt Objects.

The researchers say that more studies are needed to determine the accurate measurements of the moon’s orbit so they could conclude if it’s circular or elliptical. Moreover, this could also help them identify the moon’s origin. In other words, if its orbit is circular, it means that the moon is a result of a collision between the icy dwarf planet and another Kuiper Belt Object. On the other hand, if it has an elliptical orbit, it can only mean that the moon is likely to be a captured object from the Kuiper Belt.