Final frontier.This January, NASA scientists plan to launch a revolutionary space probe. New Horizons is set to become the first spacecraft to pass by Pluto Pluto, in astronomyPluto, in astronomy, a dwarf planet and the first Kuiper belt, or transneptunian, object (see comet) to be discovered (1930) by astronomers. Pluto has an elliptical orbit usually lying beyond that of Neptune. Although Pluto was long regarded as a planet, since the discovery (beginning in 1992) of other Kuiper belt objects, including one with a diameter larger than that of Pluto, astronomers have recognized the need to reclassify Pluto,, the only planet in the solar system yet to be studied close-up.Because Pluto is the farthest planet from Earth, astronomers know very little about it. For example, last October scientists announced that the planet has three moons. That's two more than previously thought. New Horizons, a 450-kilogram (1,000-pound) probe, will map the surfaces of Pluto and its moons and study their compositions. These celestial bodies--made from the icy material left over when the other planets formed--may hold clues as to how the solar system developed. |
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