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Today, Pluto is called a dwarf planet. A dwarf planet is round and orbits the sun just like the eight major planets. But unlike a planet, a dwarf planet does not have enough gravity to attract all of the space dust and tiny objects in its path.A dwarf planet also is much smaller than a planet, but it is not a moon.n 2006, NASA launched New Horizons, which is the first mission to Pluto. New Horizons is a spacecraft about the size of a piano that is flying to the outer edge of the solar system. The spacecraft will take nine years to reach Pluto. In 2015, New Horizons will spend more than five months studying Pluto and its moons.
Since its discovery in 1930, Pluto has been a bit of a puzzle: 1  It's smaller than any other planet -- even smaller than Earth 's moon. 2  It's dense and rocky, like the terrestrial planets (Mercury, Venus, Earth and Mars). 3  Pluto's orbit is erratic. 4  One of its moons, Charon, is about half Pluto's size.ere's how Resolution 5A defines a planet: Pluto is relatively round and orbits the sun, but it does not meet the criteria because its orbit crosses Neptune's orbit. Critics of the resolution argue that other planets in the solar system, including Earth, have not cleared the neighborhood around their orbits.