It takes 248 Earth years for Pluto to complete one orbit around the Sun. Its orbital path doesn't lie in the same plane as the eight planets, but is inclined at an angle of 17°. Its orbit is also more oval-shaped, or elliptical, than those of the planets. That means that sometimes Pluto is a lot nearer to the Sun than at other times, At times Pluto's orbit brings it closer to the Sun than Neptune. The last time this happened was from 1979 to 1999. It won't happen again until 2227.
Like the planet Uranus, Pluto rotates on its side, its axis tilted about 120 degrees.
As Pluto moves closer to the Sun, ices on its surface warm slightly and sublime ("evaporate" from solid to gas) to form a thin, mostly nitrogen atmosphere. As it moves away from the Sun, the gases cool and refreeze. The atmosphere may vanish as Pluto moves farther from the Sun.
Many Hubble Space Telescope images were combined to create these views of Pluto's surface. Distinct geologic features can't be seen, but the colors may indicate different surface compositions. When compared with earlier observations, these images suggest Pluto's face may change through time, perhaps due to seasonal changes in surface ices.
NASA, ESA, SRI (M. Buie)
