Hubble discovers new moon

A small moon has been discovered orbiting Makemake, a dwarf planet in the Kuiper belt, by the Hubble Telescope.

Provisionally named S/2015 (136472) 1 and nicknamed MK 2, it is estimated to be 100 miles in diameter. It was seen about 13,000 miles from the dwarf planet in April after several previous searches around Makemake had revealed nothing.

Alex Parker, from the Southwest Research Institute in Colorado and a member of the observing team, said: “Our preliminary estimates show that the moon's orbit seems to be edge-on. That means often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake.”

This moon increases the similarities shared between Makemake and Pluto. Makemake is two-thirds the size of Pluto and both are covered in frozen methane. Further investigations will be undertaken to see if their bulk compositions are similar also.

As the moon’s orbit is still unknown, more observations with the Hubble telescope are needed to determine if it is circular or elliptical. The orbit of the moon is important as it will explain its origin. A circular orbit suggests a collision between Makemake and another Kuiper Belt object. If elliptical, it is likely to be a captured object from the Belt. Preliminary estimates indicate that if it is a circular orbit, it orbits Makemake in 12 days or longer.

March Buie, team leader at the Research Institute, said the new discovery opens a new chapter in comparative planetology in the outer solar system.

The write up was submitted to Astrophysical Journal Letters.