The Planets
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Planets: The planet count in our solar system has gone as high as 15 before new discoveries prompted a fine tuning of the definition of a planet. The most recent change was in 2006 when scientists reclassified Pluto as a new kind of object - a dwarf planet.
Solar System Exploration: Planets
Your Weight on Other Worlds
Ever wonder what you might weigh on Mars or The Moon? Here's your chance to find out.