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Pluto is the farthest planet from the Sun and also the smallest. Pluto is smaller than seven of the solar system's moons (the Moon, Io, Europa, Ganymede, Callisto, Titan, and Triton)
Pluto is the only planet that has not been visited by a spacecraft. Even the Hubble Space Telescope can resolve only the largest features on its surface.
There are some who think Pluto would be better classified as a large asteroid or comet rather than a planet. Some consider it to be the largest of the Kuiper Belt objects.
Pluto's orbit is highly eccentric. At times it is closer to the Sun than Neptune. Pluto rotates in the opposite direction from most of the other planets.
Pluto is probably a mixture of 70% rock and 30% water ice much like Triton. The bright areas of the surface seem to be covered with ices of nitrogen with smaller amounts of (solid) methane, ethane and carbon monoxide. The composition of the darker areas of Pluto's surface is unknown but may be due to organic material or photochemical reactions driven by cosmic rays.
Little is known about Pluto's atmosphere, but it probably consists primarily of nitrogen with some carbon monoxide and methane. Pluto's atmosphere may exist as a gas only when Pluto is near its perihelion.
Pluto can be seen with an amateur telescope but it is not easy. |
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