Why is Pluto called a dwarf planet and not a comet?

[Ignacio Upton]

In terms of its orbit and physical composition (and location) Pluto is definately NOT a planet, but a comet. It's one of many Kuiper Belt objects, and not the largest either. However, I'm wondering why the scientific community doesn't just call it a comet now, instead of awarding it the dubious title of "dwarf planet?"

[baldguy]

1. b/c the defintions set by the IAU are arbitrary.

Pluto is round & it orbits the Sun. It's a planet.

[Ignacio Upton]

2. But so do many comets

And Pluto's orbit is highly eliptical, just like the Kuiper Belt objects. Its composition is also consistant with Kuiper Belt Objects. The only planets that can really form that far out are the Jovians. Pluto also has Charon as its "moon," but several other Kuiper objects have moons/sattelites.

[Hosnon]

11. The definitions are not completely arbitrary. And they include more elements than

roundness and solar orbiting.

[Canuckistanian]

3. For one thing, a comet is composed mostly of ice

Pluto seems to be rocky.

And for another point, comets have highly elliptical orbits that bring them close to the sun, where that ice core melts and leaves the "trail" that all of us on Earth can see.

But, as far as being an inconsequential body circling the sun, Pluto might just as well be a comet.

I've even heard that there is a bigger object than Pluto orbiting the sun, but it hasn't been granted the "planet" title yet.

[lordsummerisle]

4. It doesn't have comet-like behavior

it orbits like a planet. There are other solar system bodies that are suspected to be former comets as well...

[Ignacio Upton]

5. Kuiper Belt comets vs. Oort Cloud comets

The Kuiper Blet objects tend to be more stable, since they didn't have Jupiter and Saturn to hurl them around out of their original location. Most of the Oort Cloud comets act in an unstable fashion (ie. clockwise orbits and orbits that send them into the inner solar system.) Since Pluto was formed in the Kuiper Belt, it doesn't act like, say, Hailey's Comet or Hale-Bopp Comet.

[Phredicles]

6. Isn't it way too big to be a comet?

I don't know of any definitions that specify size, but I believe all identified comets are well under 100 miles in diameter. I think.

[longship]

7. Because...

A comet is a dirty iceball and a planet--even a dwarf one--is not.
Whatever it is, Pluto is decidedly *NOT* a comet.

And by the way, the designation of Pluto as a planet was rescinded because there are many other objects which orbit the sun which would then qualify as a planet. It was to keep things sane that Pluto is no longer considered a planet.

BTW, Pluto (2274 km) is smaller than Earth's moon (3476 km). Not much of a planet, if you ask me.

Also, there's the issue that Pluto's radical orbit indicates its origin as a captured object, not one of the original planets.

Pluto ain't a planet. Live with it.
;-)

[TechBear_Seattle]

8. It meets the definition of dwarf planet, that's why

There is precedent for "demoting" planets, after all: Ceres was a planet for 50 after it was discovered, then it was demoted to an asteroid and now it, too, is a dwarf planet.

[Phoonzang]

9. I don't know what you mean...

Pluto is a planet, and will always be a planet. I hear people mention this IAU....who are they? They sound rather small and insignificant. I think I'll classify them as a dwarf organization. :sarcasm:

[NNadir]

10. We are trying to humiliate Pluto.

Calling it a comet implies brilliance, interest, excitement. We don't want that.

That's not what we have in mind for Pluto, which - let's face it, is icy and dark and mean to us. It's probably a Republican.

Pluto is a dwarf. Dwarf! OK? A little tiny, weeny, puny, whiny, withered, shriveled little bit of planet, not a studly planet like, say Uranus, or Mars or a babe-a-licious planet like Venus. It's a dwarf, an eensie, teensie, miniscule planet, microscopic, not virile. A truckload of viagra couldn't save Pluto.

It's time to get even with Pluto for all the nasty things it's done. This ridicule has been too long in coming from my viewpoint.

[mainegreen]

12. It's probably a Republican?!?!?! 111!

:rofl:

[Swede]

13. Pluto is a Mickey Mouse planet.

nt

[FogerRox]

14. When Pluto was 1st discovered it was called a planet.

More recently its found to be not really a planet. But 300 million people on this planet are used to calling it a planet so I guess we'll keep calling it a planet, recently changed to a dwarf planet, so as to not suddenly freak 300 million people out. GIve it another 20 -30 yrs, they'll change the name to a icey dwarf planet. Then by 2050 it'll be a icey comet dwarf planet......

But by then we will be using it as a way station, so then it will be space station #9.

[Ptah]

15. Pluto orbited poorly

Pluto's been tombstomed

[Vidar]

16. Because Pluto is a dog, not a reindeer.