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Pluto was discovered in 1930. At that time, there wasn't
really a definition for what a planet was. We didn't know as much
about space as we do now.
In the summer of 2006, scientists of the IAU, or the International
Astronomical Union, met to discuss the naming of new objects in the
solar system.
At this time, the members agreed to remove Pluto from the list of
planets. It is now known as a "dwarf planet." A dwarf planet is not
a planet. |
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Pluto is less than half the size of any other planet. It is very
different from the other gas giants, the nearest planets to it.
It is about one-sixth the size of Earth and about
1/100 the size of Jupiter. It is made of rock and ice. Pluto is like
a comet, not a gas giant.
Ceres is another
"dwarf planet.".
It is much nearer than Pluto. It is in the asteroid belt. Ceres is
made mainly by rocks with some "dirty ice" in the surface
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