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Pluto is a dwarf planet, a large member of the Kuiper Belt. Just a few years ago, Pluto was considered a planet, but it lost its planetary status in 2006. And when it was a planet, Pluto was the most distant planet from the Sun. So how many miles is Pluto from the Sun? Pluto orbits the Sun at an average distance of 3.67 billion miles.
I say average distance because Pluto follows a highly elliptical orbit around the Sun. An object’s average distance from the Sun is called it’s semimajor axis. At the closest point of its orbit, called perihelion, Pluto is 2.757 billion miles from the Sun. And then at the most distant point of its orbit, Pluto gets as far as 4.583 billion miles from the Sun. Pluto’s orbital eccentricity is 0.2488.
One interesting feature of Pluto’s highly elliptical orbit is that it brings it closer to the Sun than Neptune. For about 20 years out of its 247.68 year orbit, Pluto comes within Neptune’s orbit. The last time this occurred was on January 21, 1979. It become more distant from the Sun than Neptune again on February 11, 1999.
Pluto’s dynamic orbit also causes its atmosphere to change dramatically. When the dwarf planet is closest to the Sun, it maintains a thin atmosphere of nitrogen, methane and carbon monoxide. But as Pluto moves further away from the Sun, its temperature drops down, and the atmosphere freezes out and falls to the ground as snow.
We’ve also recorded an episode of Astronomy Cast dedicated to Pluto. Listen here, Episode 64: Pluto and the Icy Outer Solar System.