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Solar System Shrinks with Pluto's Demotion

Leading astronomers declare that Pluto is no longer a planet, shrinking the solar system from nine planets to eight.

Pluto was discovered in 1930. It lost its planetary status when the International Astronomical Union approved a definition for planets that Pluto fails to meet.

Pluto will now belong to a new category of "dwarf planets," similar to what long have been termed "minor planets."

Earlier this year NASA launched the New Horizons spacecraft on a 9 1/2 year journey to Pluto. The probe will allow scientists to better understand the distant body.

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