Pluto is far away from the Sun, so you'd think it should be cold - but it's actually colder than astronomers were expecting. Its temperature was taken using the Submillimeter Array (SMA) on Mauna Kea in Hawaii, which was able to distinguish between Pluto and its moon Charon. Pluto is about 43 K (-382 degrees F), while Charon is 10 degrees warmer. Scientists think that heat from the Sun is converting nitrogen ice on Pluto to gas, which cools it down, similar to evaporation effect when something wet feels colder.