Pluto - Next Sign - Back to Planet Walk

The picture above, of Pluto and its moon Charon, is 50 times larger than the scale of this model. 
Courtesy NASA

    Pluto is the most distant object in our Solar System that is considered to be a planet, orbiting the Sun at an average distance of nearly four billion miles. Pluto is the smallest planet in the Solar System, 1/5 the diameter of the Earth, about the same size as our Moon, and 2/1000 the mass of the Earth. Pluto has one known moon, Charon, half the radius of Pluto and 1/7 Pluto's mass. Because of their similarity in size, Pluto and Charon orbit each other.

    Pluto's orbit is significantly different than the other planets, it is a longer and narrower ellipse. Pluto is thus closer to the Sun than Neptune for 20 years of its 249 year orbit. Pluto crossed Neptune's orbit January 21, 1979, and was closer to the Sun than Neptune until February 11, 1999. This will happen again in September 2226. The composition (frozen Methane and Nitrogen), size, and eccentricity of Pluto's orbit make it different from the four other outer planets that are Gas Giants.
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