Why was Pluto considered the 8th planet?

Answer 1

Neptune and Pluto have different orbits. Neptune is sometimes further away than Pluto. If you read recent debates, the planet Pluto may have a different identification other than planet.

Nowadays Pluto is classed as a minor planet and isn't included as one of the eight major planets. In the past, when Pluto was included it could have been classed as either the 8th or 9th planet because the orbits of Pluto and Neptune vary so that at some points Pluto is nearer to the Sun than Neptune and vice versa.

Answer 2

It wasn't! Pluto was the ninth planet. It was the next body discovered orbiting the Sun after Neptune, so it was naturally simply added to the list of planets. However, that was in 1936, and since then we have discovered a lot more about the solar system, including the existence of many other small bodies out in the region of Pluto, so it became necessary to think more carefully about exactly what we mean by a planet, and Pluto was reclassified.

Answer 3

That's because Pluto is usually further from the Sun than Neptune is.

Incidentally, Pluto is defined as only a dwarf planet now.

Answer 4

it was never considered the 8th, but was considered the 9th for some time