Hubble spots a moon around dwarf planet Makemake

National Geographic : Since its discovery in 2005, Makemake has had an odd distinction: It was the only dwarf planet outside of the asteroid belt thought to have no moon. It has now lost that distinction. Alex Parker of the Southwest Research Institute was examining data from two hours of Hubble Space Telescope observations when he saw evidence of an object orbiting the dwarf planet. The data have already revealed that the moon is 160 km in diameter. Further observations of the moon should provide clues as to whether it formed in place around Makemake or was pulled in by the dwarf planet’s gravity. More data could also provide information about the moon’s mass, which would then allow for more accurate calculations of Makemake’s mass and density. The discovery of the moon explains an unusual variation in Makemake’s heat signature that did not correlate with any warm, dark areas on Makemake’s otherwise brightly reflective, ice-covered surface.