The are three types of planets in , to answer the question we need to define the types. I am not considering Extrasolar Planets as they are not in this Solar System. Three types are :-
So lets consider each of them in turn.
Pluto would be the hands down winner had it not been been demoted as a result of a vote at the International Astronomical Union meeting in 2006. A vote had been called on what consituited a planet after the discovery of Eris. Eris was at one time considered to be larger than Pluto which is what prompted the vote. Some people called the vote a fudge and disagree with it.
The farthest planet from the Sun that has life on it is Earth. It is the only planet in the Solar System that has life and is therefore the de facto winner of closest planet to the Sun with life.
The farthest Gas Giant from the Sun that we know of is Neptune. The reason why I say know of is because there is speculation that there might well be a large gas giant on the very outskirts of the solar system. The new ninth planet has yet to be discovered. It is believed to be hiding in the Taurus / Gemini location of the night sky. As the object is so far away , it is giving off very little light so we can't detect it yet.
Evidence of there being a ninth planet is that the majority of the objects that have been discovered in the kuiper belt are in the opposite direction to Taurus. It is hypothesised that something is caused the objects to go in that directions. The people behind the claim are the same team behind the discoveries of Eris and Sedna. Even though the object is believed to be a gas giant, it could be a rocky planet. N.A.S.A
The farthest dwarf planet that has so far been discovered is Eris. It was discovered by Michael E. Brown and others in October 2003. Other Kuiper Belt Objects have been found since but none as large. Eris is 96 A.U. from the Sun. 1 A.U. is equivalent to the distance between the Sun and the Earth. Eris is therefore 96 times the distance from the Sun as Earth is to the Sun.
Eris was once thought of being as large or larger than Pluto which was one of the reasons why it was demoted to dwarf planet status. In reality, Eris is just marginally smaller. Eris also the farthest known dwarf planet that has an orbiting moon called Dysnomia. When the object was first discovered, it was referred to as Xena with the moon called Gabrielle but that the name was not approved by the I.A.U.
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