The outer planets are those planets that have been discovered in the modern era. They are the planets past Saturn, which up until the last couple of hundred years was considered to be the farthest planet in our solar system.
Uranus is the next planet after Saturn. It was discovered by William Herschel in 1781. It is a gas giant that has its own ring system, but in line with this planet's rather eccentric reputation, the ring system is lateral rather than Saturn's horizontal ring system.
Neptune was the next planet to be discovered after Uranus and it too is a gas giant.
Pluto is the last planet in our solar system. It is actually a planetoid because it is so small. Charon is Pluto's moon, and these two bodies operate more like a binary planetary pair than a planet-moon configuration, the reason being that the two bodies orbit around a centre of gravity that is in between the two.
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