Fact Sheet
Ice Worlds
Pluto and its largest moon, Charon, are cold balls of ice and rock on the fringes of the solar system. In this artist's concept, the Sun shows up as a pale yellow dot, about three billion miles from the two worlds. Using a telescope in Chile, astronomers recently watched as Charon passed in front of a distant star. From these observations, they measured Charon's size with the greatest accuracy to date: a diameter of 1,207 kilometers (750 miles). The first mission to explore the Pluto system, New Horizons, is scheduled for launch no earlier than January 17. [Credit: European Southern Observatory]
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