Why has Pluto been reclassified as a dwarf planet?

Answer 1

Pluto is a dwarf planet by definition, but it is also a : * TNO or Trans-Neptunian Object - orbit the Sun outside the orbit of Neptune; once orbits are determined they are given permanent "minor planet" numbers, and if candidates for dwarf planets, they are named. * KBO or Kuiper Belt Object - inhabits the innermost of three Trans-Neptunian regions (the other two are the "scattered disc" and the Oort Cloud). * plutoid - a trans-Neptunian dwarf planet or candidate * plutino - a trans-Neptunian body locked in 3:2 orbital resonance with Neptune, such that for every 3 Neptune solar orbits, the body orbits the Sun 2 times (a important factor in maintaining orbital stability)

Answer 2

See related question for the definition of planet.

I don't know if it's logical or not, but I have my own theory on this matter.

Pluto IS a planet, since it revolves around the sun, like the other planets.

Now, if we were living on Jupiter, which is impossible because Jupiter doesn't have a surface, we would see the Earth as a dwarf planet, because it's smaller than Jupiter.

What I'm getting at is, I think that a planet can be any size. If a round ball with an atmosphere of some description revolves around the sun regularly, then it's a planet.

Moreover, Pluto has 3 moons as well, one of which, Charon, is a little larger than half of Pluto.

Answer 3

Blame Eris. Eris is the Greek goddess of discord. When Eris was discovered in 2005, it was found to be larger than Pluto. Astronomers began questioning what should be a planet. In 2006, the International Astronomical Union had astronomers discussing what makes a planet. Most agreed on the rules of a planet had to be in orbit around the sun and that it was large enough to have gravity pull it in the shape of a ball. This is called hydrostatic equilibrium. This would mean that Pluto would be a planet, so would Ceres, Eris and possibly many more Kuiper Belt objects. There was a committee of astronomers that wanted to be more specific. Pluto was less than half the size of Mercury and Eris was only slightly bigger than Pluto. They came up with a third rule about a planet must clear its orbit. This would eliminate Eris, Pluto and Ceres (and future Kuiper Belt objects.) Brother Guy Consolmagno of the Vatican Observatory was head of the committee. "Clearing the neighborhood around it's orbit" means that the planet is gravitationally dominent. Alan Stern and Harold Levinson wrote a paper on this in 2000 that was presented to the IAU. The ruling was and is controversial. It is possible that at a later time the IAU may change the decision again. Mike Brown who discovered Eris thinks that is silly to call Ceres, Pluto, and Eris planets and not call our moon a planet when it is bigger than all of them.

You may want to read Neil Degrasse Tyson's book The Pluto Files. Norton, 2009.

Answer 4

Because Pluto meets all of the requirements for classification as a dwarf planet:

1. It orbits the sun
   
2. It is in hydrostatic equilibrium
   
3. It has not cleared its orbit from asteroids and other debris
   

Answer 5

Pluto was reclassified as a dwarf planet in 2006 by the International Astronomical Union because it did not meet all three criteria required to be classified as a full-fledged planet. Pluto did not clear its orbit of other debris and its mass was not dominant enough compared to the other objects in its orbit.

Answer 6

it is a dwarf planet since 2006. it is a very small planet.

Answer 7

yes,Pluto is classified as a dwarf planet

Answer 8

Pluto is classified as a dwalf pl