|Exploring The Planets
Because of its very small size and great distance from Earth, Pluto is a very faint object, even in the largest telescopes. At such a great distance from the Sun, Pluto is exceedingly cold and virtually everything is frozen.
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NASA Artist Conception
This artist's rendition shows what the Sun might look like from the surface of Pluto. The Sun is so distant that it would appear as a bright star in the sky.
A Double Planet?
Pluto's satellite Charon has a diameter of approximately 1200 km (700 mi.) and is the largest satellite in the solar system in proportion to the size of its planet. Charon orbits Pluto at a distance of 20,000 km (12,000 mi.) with exactly the same period, keeping the same face directed toward Pluto, in what is called locked synchronous rotation. As a result, Pluto and Charon are often referred to as a double planet system.
Composition of Pluto and Charon
Scientists have been able to learn much about Pluto and its large satellite Charon using modern astronomical techniques. Scientists have found that Pluto is covered with nitrogen and methane ice. Pluto's satellite Charon however, is believed to be covered with ordinary water ice. It's not known why their surfaces differ, but Pluto and Charon are probably mostly water ice with rocky cores and a few other materials such as methane and nitrogen mixed in.
A Tenuous Atmosphere
Pluto has a tenuous atmosphere of primarily nitrogen gas with some methane gas. As Pluto's eccentric orbit brings it nearer to the Sun, frozen nitrogen and methane are warmed and form a thin gas layer. As Pluto recedes from the Sun, the temperature will fall and the atmosphere may all but disappear.
©1998 National Air and Space Museum