When was Pluto disscovered not a planet?

Answer 1

It was not so much a discovery that Pluto wasn't a planet, so much as a general concensus that it shouldn't be called a planet anymore. Over the past decade, astronomers have discovered several bodies beyond the orbit of Pluto that are in fact larger (for example, Eris.) They realized that there were probably many more they hadn't discovered yet and that the term planet was impractical for Pluto since it was so small and there were so many similar sized objects orbiting the Solar System. Eris was probably the final blow to Pluto's status. It is larger than Pluto and for a long time astronomers called it the solar system's "tenth planet''. In the face of this discovery and the fact that many other similarly sized objects had been found, the International Astronomical Union decided to formally define the word "planet" for the first time in 2006 and in the process effectively demoted Pluto.

Answer 2

Pluto's status as a planet has been in question since the early 1990s as more and more smaller but similar objects were discovered in Pluto's region of the solar system, forming what we now call the Kuiper Belt.

In 2005 astronomers discovered a new object, now called Eris, that was about the same size as Pluto. The discovery of Eris, which was a candidate for being named the tenth planet, led astronomers to come up with a formal definition of a planet in 2006. Neither Pluto nor Eris made the cut.

Answer 3

dumb people said that

Answer 4

in 2006.