NASA’s first mission to the dwarf planet Pluto is two years away from its destination.
Image Credit: NASA, ESA, and M. Buie Southwest Research Institute


What Will We Find At Pluto?

By David Darling

Something odd happened a few months after NASA’s deep space probe New Horizons was launched Jan. 19, 2006—its target got demoted from a planet to a “dwarf planet.” In September 2006, astronomers voted to downgrade Pluto so that it now falls into the same category as Ceres, previously considered the largest asteroid in our solar system. New Horizons will be the first spacecraft to conduct a flyby of what used to be the ninth planet in the solar system and its system of five known moons.

Not that Pluto’s reclassification makes it any less interesting. Even though it’s smaller than Earth’s Moon—with a diameter of only about 2,300 kilometers—it does have five moons of its own, including one called Charon, which is two-thirds Pluto’s size. Pluto also has a fascinating past, which scientists hope New Horizons will help shed some light upon.

It used to be thought that Pluto might be an escaped moon of the eighth planet, Neptune, which got kicked out when the gas giant captured a much bigger world, Triton. But there were always problems with that theory because Pluto’s orbit, although very elongated and at times bringing it closer to the Sun than Neptune, never carries it close to Neptune itself. Nowadays, astronomers recognize Pluto to be the largest member of the Kuiper Belt—a ring of objects located between 30 and 50 AU (1AU = the average distance from the Earth to the Sun) from the Sun. In some respects, Pluto is like a giant comet nucleus, and if it were brought close to the Sun it would develop a tail like that of a comet.

Read more: What Will We Find At Pluto? « AmericaSpace.

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