Because Pluto orbits much further from the Sun than Earth, it takes much longer to orbit the Sun. In fact, Pluto takes 248 years to orbit the Sun. That’s because Pluto orbits at an average distance of 5.9 billion km from the Sun, while Earth only orbits at 150 million km. In fact, it takes so long for Pluto to orbit that Sun, that the dwarf planet hasn’t even completed a third of an orbit from when it was discovered back in February 18th, 1930.
Pluto has a highly elliptical orbit. Its distance from the Sun varies from 4.4 billion km to 7.4 billion km. And during this orbital period, Pluto goes through a few interesting changes. You might be surprised to learn that Pluto has an atmosphere. When it’s at its closest point to the Sun, Pluto’s atmosphere evaporates from the surface and surrounding the dwarf planet. And then when it gets further away, the atmosphere freezes again, coating the surface in a thin layer.
Pluto was only discovered in 1930 by Clyde W. Tombaugh. Because it takes 248 years to orbit the Sun, Pluto won’t have completed a full orbit until the year 2178.
We’ve also recorded several episodes of Astronomy Cast just about Pluto. Listen here, Episode 64: Pluto and the Icy Outer Solar System.