Pluto takes the longest time of the eight planets (248 Earth years) to orbit around the sun. Because it’s the closest to the sun, Mercury has the fastest orbit, at 88 Earth days. Earth takes 365 days to orbit the sun.
Pluto is the only known dwarf planet with an atmosphere. It is very thin and would be toxic for humans to breathe. When Pluto is at its perihelion (closest to the sun), Pluto’s atmosphere is gas. When Pluto is at its aphelion (farthest from the sun), its atmosphere freezes and falls like snow.