The Researching Rhinos Present: Which planet is the coldest?

The answer to this question depends on how you define the word "planet." Until 2006, Pluto was considered the ninth planet of the solar system. Pluto is definitely colder than the other eight planets, so if you count Pluto as a planet, it wins the title of "coldest planet." Pluto's average surface temperature is -382 degrees Fahrenheit.

However, in 2006, scientists concluded that Pluto is not really a planet at all but part of a belt of icy objects called the Kuiper Belt that orbits the sun erratically outside the orbit of the planet Neptune, just like the Asteroid Belt orbits the sun in between the orbits of Mars and Jupiter. If you follow that definition, then that leaves Neptune as the coldest planet. Neptune's average temperature is -315 degrees Fahrenheit.

Here are some websites about Pluto, Neptune, and what the coldest planet is:
Views of the Solar Sysytem: Neptune
Pluto Colder Than Expected
Pluto Is Not A Planet

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