Respuesta :
Pluto was declared to be a dwarf-planet by the International Astronomical Union in 2006.
The ninth planet of the world, Pluto, was formally downgraded to a dwarf planet in 2006.
What are Dwarf planets?
A dwarf planet is a small planetary-mass object which lies in the direct orbit of the sun. It's mass is less that the eight existing planets. Dwarf planets do not fulfil the criteria of being a planet.
When were dwarf planets introduced?
The International Astronomical Union (IAU), in 2006, gave new definitions and criteria for the existence of planets. Pluto did not fulfil these criteria. Hence, it was changed to a dwarf planet in 2006.
Therefore, the correct answer is 2006.
Learn more about Dwarf Planets on https://brainly.com/question/1333253
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