When I was a kid. Pluto was still a planet. Discuss!

Question

Self-explained question. I'd like to hear random opinions.

Answer 1

if you go back far enough, a total of 35 bodies in our solar system have been classified planets.

currently, if you were to accept pluto as a planet again you would have to accept eris, ceres, and makemake, and that list continues to grow. so the total number of planets is either 8, 12, or 35. take your pick, you dont get 9.

Answer 2

Pluto is still a planet.  The IAU is full of it.  Dynamics do not belong in the definition of a Planet.  What about rogue planets?  There are hundreds of billions of them in the Milky Way (though none have been detected).

Ceres is a planet too.

The Moon is a planet.  It's also a moon.

But i'm willing to call Eris a Dwarf Planet until Mike Brown dies.  He's just being pig headed.

Answer 3

Expect the debate over Pluto to be rekindled at the next International Astronomers Union meeting next year in Rio de Janeiro, Brazil.  The IAU is the body that came up with the definition of "planet" that excluded Pluto, and a lot of astronomers aren't very happy with the current definition.

Answer 4

Pluto is too small and outside of the required gravitational field to be considered a planet. There are plenty of moons in our solar system bigger than that tiny thing! It is now an official satellite of the sun or something of that nature but no longer a planet.

Answer 5

Discuss what...?   They re-designated Pluto.  It's an international agreement.   The alternative was to find *up to 50* Kuiper belt objects the size of Pluto or larger, and assign them each a name... so, the choices are, have a 60-planet solar system (a LOT of names to remember), or re-designate some objects, and have 8 major planets and a number of dwarf planets or planetoids. (Or, the new term I heard was "Plutoids.")

Answer 6

Well I'm not all that happy for Pluto, but I can completely understand the IAU's decision to demote Pluto from a planet to a dwarf planet. It wasn't because they just ran out of things to do, they have a very good reason to do so.

In the start of the 21st century, we discovered about 3 planets in the Kupiter Belt which is the same asteroid belt that Pluto lies in. These planets included Sedna and Quouar, or sometimes refered to as "Xena". These planets had most the same characteristics as Pluto, and a former planet, Eris. Eris was discovered back in the 19th century and was considered a planet for a while, but was later demoted. After looking back on this planet and its characteristics compared to the other planets, they had most the same composition.  So either they all should be considered planets, or none of them. At first thought, three additional planets doesn't sound like a bad idea, does it? Well more of these bodies would be discovered in the Kupiter Belt. Before you know it, we are looking at 30 additional planets to the solar system. These bodies were so common that they weren't rare enough the be considered planets. So the IAU decided to vote on whether Pluto and these other celestial bodies should be considered planets or not. They met all the requirments of becoming a planet- they were all in a spherical shape as a result of hydrostatic equilibrium, they all orbited the sun, but they were in an asteroid belt. An asteroid belt could have hundreds of these things floating around. So the IAU decided to add "a planet cannot be in an asteroid belt." to their list of planetary criteria. This demoted Pluto. But should it be considered an asteroid? No, because it is in a spherical shape. So they came up with another word for bodies like Pluto, and there are probably tons of them, and called them "dwarf planets".

Due to controversy over what the criteria are for a "dwarf planet", the IAU recently decided to give them a new name with a more meaningful, understandable definition. They named them "plutoids" over their founding father, so to speak, Pluto.

The definition for a "plutoid" only applies to this solar system-

It is a spherical body that lies beyond Neptune and meets all the requirements of a planet, but is in the Kupiter Belt. It is a sub classification of a planet. There is still some controversy over it.

On the scientific level I can understand it, but on the more personal/sympathetic level, I feel sorry for poor pluto. But it does now have an entire classification named after it!

Answer 7

I grew up learning in science that there were exactly seven planets. I am only fifteen now, and I still question this. I asked my science teacher, "How can they just cut a planet out? What are they going to do with the saying on how to remember the planets?" You know the one about a mom serving nine pizzas or something. Any who, I still believe this should be a planet.