kuiper belt objects

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The dwarf planet Makemake, discovered in 2005, is cold, dark and remote. It sits in the Kuiper Belt beyond Neptune, orbiting the sun at a distance almost 46 times farther away than Earth and completing an orbit once every 310 Earth-years. Recent observation by the Hubble Space Telescope, however, has revealed that Makemake is not as lonely as it once appeared: it has a moon.

Finding a Dark Moon

Until this new discovery, scientists believed Makemake was the only one of the four officially recognized dwarf planets in the Kuiper belt (Pluto, Haumea, Makemake and Eris) without a moon - the fifth official dwarf planet, Ceres, is closer to Earth and also moonless. However, there were some inconsistencies in prior measurements of Makemake’s light and heat. Observations from the Spitzer and Herschel space telescopes revealed warm, dark areas on Makemake’s otherwise bright, cold surface. However, Makemake’s apparently mottled surface would not make sense with a normally rotating dwarf planet unless it was spinning with one of its poles facing directly toward Earth, a fairly unlikely situation. The “dark moon hypothesis” offered a simpler explanation: a charcoal-black moon orbiting Makemake. “Imagine that the dark material isn’t on Makemake’s surface… it’s in orbit!” image analysis lead and paper coauthor Alex Parker tweeted. “If the moon is very dark, it accounts for most previous thermal measurements!”

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