Pluto is not a planet in our solar system as of what year?

Pluto was discovered in 1930, this changed in 2006 with the adoption of a formal definition of planet by the International Astronomical Union (IAU).

The issue of a clear definition for planet came to a head in January 2005 with the discovery of the trans-Neptunian object Eris, a body more massive than the smallest then-accepted planet, Pluto.

In its August 2006 response, the IAU, recognized by astronomers as the world body responsible for resolving issues of this nature, released its decision on the matter during a meeting in Prague in the Czech republic.

This definition, which applies only to our Solar System, states that a planet is a body that orbits the Sun, is massive enough for its own gravity to make it round, and has "cleared its neighbourhood" of smaller objects around its orbit.

Under this new definition, Pluto and the other trans-Neptunian objects do not qualify as planets. The IAU's decision has not resolved all controversies, and while many scientists have accepted the definition, some in the astronomical community have rejected it outright.