Why is Pluto's orbit different compared to other planets, and why....

Question

..does this difference cause it to sometimes be inside of Neptune's orbit and sometimes outside of Neptune's orbit???

Answer 1

Pluto's orbit is very different. It's highly elliptical, travelling around the Sun in a squashed circle. And Pluto's orbit is highly inclined, travelling at an angle of 17-degrees. This strange orbit gives Pluto some unusual characteristics, sometimes bringing it within the orbit of Neptune.

Pluto's orbit is also highly inclined. This means that it doesn't orbit within the same plane as the rest of the Solar System. Instead, Pluto orbits at an angle of 17-degrees. For part of its orbit, Pluto is above the plane of the ecliptic (where the other planets orbit) and other times it's below that plane.

Because Pluto's orbit varies so widely, it can switch places with Neptune, orbiting closer to the Sun.

Answer 2

Pluto has an orbit more eccentric or more elliptical than most planets. This causes it to be closer to the Sun than Neptune sometimes.

This is probably due to their being less matter in the outer edges of the solar system during the formation of the planets. The inner and most of the outer solar system had a lot of matter flying around collecting into the planets we all know and love today. All that flying space debris collecting togethor averaged out their tangential inertia so the orbits were nearly perfect circles. Pluto was very far out and is composed of much less matter so it had less of a variety of initial inertia vectors to average out its orbit.

Answer 3

Do you mean "why", or "in what way"

Pluto's orbit is both elongated (more elliptical) and inclined to the plane of the planets' orbits.

It is because of this elongated orbit that it crosses Neptune's path.

As for why - that's down to the dynamics in the nebula from which the solar system formed....

Answer 4

The orbit of Pluto is unusual in several ways. It is inclined more than 17° from the ecliptic (the plane in which the orbits of the planets lie). The orbit is also more eccentric (far from circular) than any other planetary orbit. At times, Pluto is closer to the Sun than the orbit of Neptune.

Every 228 years, Pluto's orbit brings it closer to the Sun than Neptune for a period of 20 years. From 1979 to March 1999, Neptune was the farthest planet from the Sun.  

Since Pluto is no longer a planet, but a plutoid, because it is outside the orbit of Neptune and in the Kuiper Belt (part of the IAU's new planet definition), that would mean that Neptune is the farthest planet from the sun anyway.  It raises an interesting point, though.  For the 20 years that it is closer to the sun than Neptune, it would fit the definition of a planet.