Pluto...Why did they change it?

Question

What did Pluto do that they decided to take the status of "planet" away? I know it seems to fit the status of Dwarf Planet, but why were they looking to change its status? Did they discover something else that made them look at all the planets.
Asked by a 3rd grader, and I can not find an answer.

Answer 1

A new celestial body was discovered in 2005 (2003 UB313) that was found to be larger than Pluto. This left astronomers with a conundrum. Do we label all bodies of this size as planets, or demote Pluto?

As they decided that there could be more of these dwarf size planets, it was decided to demote the 9th planet to the aforementioned "Dwarf Planet".

Ironically, 2003 UB313 was named "Eris" after the greek goddess of strife, due to the problems it caused!

Answer 2

Pluto.
When Pluto was first discovered it was thought by some to be bigger than the Earth. Since then better measurements have shown it to be much, much smaller. Recently more objects about the same size have been found. They were really too small to be called planets but since they were around the same size as Pluto, either they had to be called planets or Pluto had to be demoted to be consistent. At the recent meeting of the International Astronomical Union the non-unanimous vote was that it was no longer to be called a planet.

Scientists reclassify things all the time as better information comes in. Usually they reclassify bacteria, plants or sometimes animals or rocks. This almost never makes the news even though it is more likely to be important to us because these things are here on Earth. Pluto is a very long way away and as recently as 1929 nobody even knew it was there.

The only people who have a right to have an opinion on this are those with detailed knowledge of the solar system and astronomical classification schemes. What anybody else thinks actually does not count.

Answer 3

When Pluto was first discovered, astronomers were looking for an explanation for some small wobbles in the orbits of Neptune & Uranus. After the initial excitement, they realized it was too small to have such an effect. In fact, its orbit was so lopsided and crooked, they didn't feel all that comfortable calling it a planet, but it did go around the Sun and there was nothing else like it out there. So it was dubbed a planet.

With the discovery of several small, rocky objects with crooked orbits, such as Eris, Quaoar, Sedna, Varuna and a host of bodies that don't even have proper names yet, Pluto was no longer unique. It looked and acted more like them than the other planets. So the astronomers decided to change its status. Pluto is now the first of a bunch of "Kuyper Belt Objects" or "dwarf planets". Perhaps they'll find a better name for them as they become more familiar with them.

Pluto hasn't gone anywhere or changed at all. We're just learning more about it and its area of the Solar System. (It's kind of like when Fred the cat has kittens and you change "his" name to Frederica.)

Answer 4

Well for starters, Pluto is just too small. In the neighborhood where Pluto lives? Planets are supposed to be huge. The Jovian planets, Jupiter, Saturn, Uranus and Neptune are 20 to 300 times the size of the Earth, and Pluto is really small compared to the Earth, smaller than our Moon. Kind of stands out.

And Pluto is not made out the same material as the Jovians. The large planets are mostly gigantic spheres of gas, mostly hydrogen and helium. Likely there are no solid surfaces, only denser and denser gas all the way in. Pluto is a small solid world of methane, water, carbon dioxide and ammonia ices, maybe a little rock and with a just hint of atmosphere (that freezes out and falls as snow in her "winter").

And third, Pluto's orbit is the most eccentric (oval shaped) and the most tilted to the plane that the rest of the planets orbit in. Also, Pluto is locked in a resonance with Neptune's orbit and comes closer to the sun than Neptune sometimes.

There were theories that Pluto was a lost moon of Neptune but that was before we discovered she also has one large moon (Charon) half her size (pretty much, this system is a double planet) and recently two other teeny-tiney moons (Nix and Hydra).

Pluto seems like she cant be an ejected moon-she must have formed on her own and seems to be part of an entire army of small icey-dwarf objects that circle just outside Neptune's orbit in what is known as the Kuiper belt. We have no idea of how many or how large these objects may be. NOT "planets" proper, hence the new term "dwarf planet" where Pluto is king.

BUT I still think Pluto should be called a planet because of historical reasons (discovered by an American, financed by Percival Lowell, Tombaugh's life story, etc).

Answer 5

The International Astronomy Union defined the term "planet" scientifically. Pluto does not have the necessary characteristics to be a planet; however it is to big to be an asteroid and has a natural satellite too.

So, Pluto becomes a dwarf planet, along other Trans-Neptunian objects like Eris (another dwarf planet and bigger than Pluto) and Sedna.

Answer 6

They changed the status of Pluto becasue astronomers now know that its orbit crosses the orbit of uranus. The other planets has very defined orbits around the sun and each orbit is separate and distinct from the others.

Since it takes over 240 years for Pluto to go around the sun, it took current advances in astonomy to figure out that its orbit crosses another planets orbit.

The last time pluto was in the same positions it is now was in 1759.

Answer 7

Well, they were finding more and more objects that were like Pluto with the more powerful telescopes that we have today and one that was even bigger (Eros) so instead of going to what would probably be 20 or more planets eventually, they simply demoted Pluto to match the other objects that were like it.

Answer 8

Pluto was changed because, it wasn't really a planet to begin with. It was proposed that it be a planetoid at first. but sombody wanted to be famous and woosh. now that we have more objects like it, we have put pluto in its rightful place.

Answer 9

Pluto will always be a planet. Let astronomers dawdle; the identity of the cosmos is cultural, hardly scientific.

Answer 10

Sadly - it seems it was changed so a load of astronomers could justify an expense account. I agree - the naming of planets is a cultural and historical, anthropological affair - and busy-body 'scientists' should keep their noses out. It'll always be a planet - until mankind is gone.