Pluto: The Ice Planet
	Pluto is actually smaller than one of Neptune's moons, Triton.

Pluto is usually the farthest known planet from the Sun. It has a very unusual orbit. Once every 248 Earth years, Pluto swings inside the orbit of Neptune. It stays there for twenty years. During those twenty years, Pluto is closer to the Sun than Neptune. While it is closer to the Sun, Pluto has an atmosphere. The methane and nitrogen frozen at the poles thaw out, rise, and temporarily form an atmosphere. As it moves toward its farthest point from the Sun, Pluto's atmosphere freezes and falls back on the surface of the planet. Pluto has only one known moon. Pluto's moon, Charon, is half the size of Pluto. Some astronomers call Pluto and Charon a double planet because they are so close in size. Other astronomers do not think Pluto is a real planet at all. They think it may be a moon which escaped from Neptune's gravitational pull .

A Question Why is Pluto sometimes called a double planet?