Why is Pluto no longer considered a planet?

Answer 1

In August 2006 the IAU redefined the term "planet", and classified Pluto, Ceres, and Eris as dwarf planets. Pluto is also classified as the prototype of a family of trans-Neptunian objects. After the reclassification, Pluto was added to the list of minor planets and given the number 134340.

The 2006 definition of "planet" by the International Astronomical Union (IAU) states that, in the solar system, a planet is a celestial body that:

1. is in orbit around the Sun,
2. has sufficient mass so that it assumes a hydrostatic equilibrium (nearly round) shape, and
3. has "cleared the neighborhood" around its orbit.

A non-satellite body fulfilling only the first two of these criteria is classified as a "dwarf planet", whilst a non-satellite body fulfilling only the first criterion is termed a "small solar system body" (SSSB). The definition was a controversial one, and has been both criticised and supported by different astronomers.

According to the definition there are currently eight planets and three dwarf planets known in the solar system. The definition does not apply outside the solar system, and so does not include provision for extrasolar planets. Exoplanets are covered separately under a 2003 draft guideline for the definition of planets.

Answer 2

Because a group of astronomers at Caltech are discovering other objects similar to Pluto in our outer solar system. The most recent, Eris (formerly Xena) is actually larger than Pluto and has at least one moon. Where do you draw the line at what is a planet and what is an asteroid or minor planet? It was decided that Pluto bore more similarity to these other smaller objects than to the other planets which are all relatively large and are clser to the sun than Pluto.

Answer 3

So far we've seen no verifiable evidence of other sentient species. That said, I believe with some certainty that somewhere in our galaxy at some past, present, or future time, a sentient species did/does/will exist.

Why haven't we heard from them?

Perhaps they are not technologically advanced enough to be heard. They may be mastering stone knives right now, or experiencing their own Rennaisance.

Perhaps they are here right now. Any species sufficiently advanced to travel interstellar distances would be able to hide or masquerade with ease. That Boeing 737 that just flew by may be a surveillance craft.

Perhaps they are so far away they will never notice us and vice versa.

Perhaps they existed a million years ago and died out.

Perhaps they will exist a million years from now.

It is really impossible to know for sure.

The Drake Equation suggests that there is sentient life out there. The Fermi Paradox casts doubt. Play around with the calculation form at the second link and see what you think.

Answer 4

they said it was to small ,but now they call it a planet again ,so they have to incould the other two masses out there that are bigger that pluto which means we now have 11 maybe 12 planets . plus some of the moons are bigger that pluto this makes it even harder to really call them planets but they do orbit the sun in a round about way

Answer 5

Pluto is a planet except it is not in the main category...
It is called a dwarf planet aloong with some others...
Now we have only 8 planets. Look at this:
First it used to be this:::

My
Very
Elegant
Mother
Just
Served
Us
Nine
Pizzas

but now it is:::

My
Very
Elegant
Mother
Just
Served
Us
Nachos

lolz....

Answer 6

pluto is no longer considered a planet because it's only satellite is nearly the same size as it and the fact that in the course of its orbit it overlaps neptune's orbit. as a planet it is not meant to interfere with the orbits of other planets

Answer 7

It's too small

Answer 8

cause it was ALWAYS nothing more than mickey mouse's cute doggy