Why have astronomers decided that pluto should be reclassified as a dwarf planet?

what happens to most meteors when they enter earth's atmosphere?

They agreed a new definition of a planets and created "dwarf planets" as a separate type of object. Pluto qualified only as a "dwarf planet", because it is not the dominant object in the neighbourhood of its orbit ...

There is a new standard of planets that the IAU set in 2006 and Pluto did not pass it. The new qualification is that a planet must be free of debris around it.

Most meteors are small enough to be burned by friction once it enters the Earth's atmosphere. They are also called 'shooting stars'.