Why is Pluto to called a dwarf planet?

Answer 1

Pluto is considered a dwarf planet because A., it is the smallest planet (now not considered a planet anymore) in the Milky Way and B., because a larger planet was discovered to be behind it. Therefore, Pluto is no longer officially a planet, and is now a "dwarf" planet, compared to the others.
Pluto was discovered in 1930, and recognised then as being the ninth planet. Over more recent years though, more and more objects like Pluto were discovered further out. They approached the size of Pluto, or in the case of Eris, thought to be even larger.

Astronomers were faced with a dilemma, either we kept adding planets to the list, or we had to redefine what a planet actually was. In 2006, a new definition for a planet was established. It had to be approximately round, it had to orbit the sun and it had to have cleared its orbit of all other objects - so that at that distance from the sun, there were no other sizable bodies. Pluto is not large enough to have done the latter, while all other remaining planets have, so it was downgraded to a dwarf planet.

Answer 2

Pluto is considered a dwarf planet because it didn't meet all the criteria for being a planet. Here are the criteria:

it orbits the sun (Pluto does that)

is nearly round in shape (check)

has cleared its neighborhood of other planets (Saturn crosses Pluto's orbit every so many years, so Pluto fails this criteria)

Answer 3

Because it meets all of the requirements of a dwarf planet:

1. Pluto orbits the Sun
   
2. Pluto is ball-shaped
   
3. Pluto orbits in the presence of asteroids and other debris
   

Answer 4

Pluto is a dwarf planet because it isn't big enough to be a major planet. (Earth, Mars, Mercury, etc.) There are other dwarf planets in our solar system, too.

Answer 5

this is because it is the most smallest planet in the solar system

Answer 6

because it is inhabited by midgets

Answer 7

because its smaller and older

Answer 8

because it is very small