Astronomers have announced that the distant dwarf planet Makemake has a moon. Makemake orbits beyond Pluto in the Kuiper belt region of the solar system and—along with Pluto, Eris, and Haumea—is one of four dwarf planets found there. Makemake was discovered in 2005 and was thought, until now, to be the only one of the four without a moon. The moon was discovered in Hubble Space Telescope images taken in 2015 and has been provisionally designated S/2015 (136472) 1. (S is for satellite, 2015 is the year of discovery,  is Makemake’s numerical designation, and 1 is for the first satellite discovered in 2015.) The moon’s orbital plane is nearly edge-on to Earth, so it has likely been hidden in Makemake’s glare until now. Previous observations of Makemake had suggested that it has a two-tone surface—mostly very bright but with a small very dark part. However, the moon’s discoverers have speculated that the dark component could actually have been S/2015 (136472) 1. They further speculated that, unless the moon was an object captured by Makemake, it likely came from a giant impact, meaning that such collisions are common in the Kuiper belt.
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