why is neptune not pluto the farthest planet until 1999?

Answer 1

First of all, Pluto is no longer officially a planet. To answer your question though, the reason Neptune is sometimes the most distant planet (..even farther out than Pluto..) is simply because of the nature of their orbits around the sun and their relative nearness to each other.

Answer 2

Pluto has an "eccentric" orbit which means that it varies a lot in its distance from the sun. Sometimes it is closer to the sun than Neptune; at other times it is further away from the sun.

In any case, Pluto is no longer considered a major planet, so Neptune is the furthest major planet from the sun.

Answer 3

Pluto has always been considered the farthest planet from the sun. Now pluto is no longer considered a planet, by some, if not all scientists. That is why Neptune is considered the farthest planet from the sun now.

Answer 4

Pluto's orbit is so eccentric that for a while Pluto is closer to the sun than Neptune

Answer 5

Neptune and Pluto have a bizzare arrangement. Although they both revolve around the sun, the orbit of pluto is more elliptoid and will penetrate the orbit of Neptune.

Answer 6

It is due to the eccentricity of their orbits. Since their orbits are elliptical, at times they are closer or further from the sun. At their most extreme they can trade places.

Also, as of late last year, Pluto is no longer an official planet. Check out the link below.
http://news.nationalgeographic.com/news/2006/08/060824-pluto-planet.html

Answer 7

Every now and then, Neptune and Pluto switch places, I think.

Answer 8

Planets have eccentric orbits, not circular, and if their distances from the Sun are not too dissimilar, and the eccentricity great enough, the one that is usually closer, may, for a short time, be further away.