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Terminology is still controversial. Objects that do not quite qualify as planets - because they are big enough to be round but not big enough to dominate their neighbourhoods - might become "dwarf-planets" or planetoids. These would include Pluto and Ceres, the largest asteroid. And the small fry of the solar system, such as asteroids, might be called small solar system bodies, or retain their current designation as minor planets.
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The fuss over Pluto's planethood started a few years ago when astronomers began to discover large, icy bodies in the outer solar system, some of them not much smaller than Pluto. Then in 2005 came the killer: the object designated 2003 UB313, popularly known as Xena, is 2400 kilometres across, making it slightly bigger than Pluto. Should it be called the tenth planet? If so, how many more planets might there be? Nobody had a clear definition of the term.