Should Pluto be classed a planet?

Yes, Charon (because the barycentre of the orbit lies outside the sphere of Pluto).

Pluto would be (officially) a double planet!

So you would re-define Asteroids, comets, Kuiper Belt objects and objects within the Oort Cloud, as planets?

Nope but then i dont know muh about the solar system save the 10 planets and one big asteroid belt inbetween mars and Jupiter.

On this one bun i pass the torch to you as i dont really know more than what several sci-films and my school science class have taught me lol

Nope, sorry. I'd like a definition that ignores orbital characteristics entirely. No-one declares galaxies not to be galaxies because they orbit other galaxies, or stars not to be stars if they orbit another star. But a planetary body that orbits another planet? 'moon' . Tsk.

Haha, wooo! Well I'm studying this at Uni so I am in my one and only element



In essence then you would be willing to define anything big enough within our own solar system, as a planet? I really don't like that idea to be honest, I think it would be ridiculous to class an Asteroid under the same definition as Jupiter And as for moons, well they don't even orbit the Sun! Surely the most basic criteria (before size...) is that they orbit the sun? Moons are just satellites of a planet, they really have nothing to do with the Sun, if you picked up that planet and it's moon system and plonked it in another solar system, that planet would now orbit the new Sun, but the moon system wouldn't care, it'd keep orbiting that same planet

Surely the science would become much less exact if you de-categorised everything and plonked it all together, completely neglecting the distinct characteristics of each group and pretending they're all the same? It just seems like a waste of time to be honest

But surely the only wy to distinguish between two objects being a Moon and a Planet is to look at their relative size. For example with the Earth and our Moon, theEarth is much bigger.

But in reality, don't the Earth and the Moon also orbit each other, like Pluto and Charon do? Only due to the huge difference in size between the Earth and our Moon it is much less noticeable with the Moon appearing to orbit the Earth, probably because the point the both orbit each other around is actually inside the Earth.

So why should we make a distinction solely based on size like this?

A similar thing happens between planets and te sun, they orbit each other around another point, again, it's almost unnoticable and appears like the planets only go around the sun (I'm sure we were told all this in my Intro to astrophysics module at uni). So then you really need other criteria to identify a star from a planet, such as nuclear fusion taking place within the object, or at least being extremely massive (if we are to consider thinks like brown dwarfs potentially being stars (are they normally classed as stars or planets? and they don't actually have and fusion taking place in them do they?).

its the little quirks in science that make it so entertaining, i say yes!

But the Earth orbits the Sun whereas the moon technically does not...no?

i think its a bit late to change it now, my younger brother would be gutted. anyway, whatever its called, it is what it is

IU thought the plan was to keep it as a planet but make a new category of planet called 'plutons' including ceres the asteroid pluto charon and the largest kuiper belt objects. this way its still a planet but kinda not. neat hey?

How is this science? This is astro-geography (cosmography?). Nothing new is being observed, it's just renaming an existing phenomena.

This is a very important topic for discussion. It is vital that we set a precedent for naming Pluto-sized stellar-orbit objects. That way we can quickly and easily decide exactly how many planets any given system has, which is vital for the long-distance space tourism industry. Imagine the stink if Thomas Cook listed Alpha Centuri as having 12 planets when in fact it only has 9 - people would sue!

Look at the path the Moon takes over the course of exactly one year, it'll be back exactly where it started from one year earlier with the path en-circling the Sun. It might not be a perfect ellipse, but then neither is that of the Earth technically due to the slight effect the Moon will have on the orbit.

I've just looked this up....they are classed as 'sub-stellar objects' as they haven't enough mass to start nuclear fusion, but have convective surfaces and interiors like proper stars do. And yeah, the have actually been identified now..which is an amazing this to say they are so small and dim and distant

What if the Earth was orbiting Jupiter? There is probably a similar, if not greater size difference between the Earth and Jupiter than between the Earth and the Moon. Would you want the Earth classified as a moon in that situation even though it would be the 6th largest object in the Solar System?

Perhaps we need to have a set of criteria which defines any object in the solar system as a planet irrespective of how it orbits the sun, so long as it does actually orbit the Sun in some way. If the Moon was to meet these criteria, then perhaps we'd need to start describing the Earth-Moon orbit as a binary-orbital planets, same as the Charon-Pluto orbit.

Just out of interest, do you know of any situation that has been observed where we have one object being orbited by another smaller object and then that smaller object is in turn? They would, if they exist, be trinary-orbital planets (assuming they all met the criteria to be planets).

But the Earth orbits the Sun whereas the moon technically does not...no?

Brown Dwarfs are classified as stars, I guess because of their composition and for the fact that had their mass been slightly larger they could have begun nuclear fusion. But they haven't been discovered yet, have they?

And you can't really say 'oh it's just because of size, that's the only difference' - size is incredibly important as of course that has a lot to do with the mass of the objects - and the mass determines the gravitational force which is what causes the orbit in the first place. In that sense I think that it is fairly reasonable for, say for example with the Earth and moon, to classify the Earth as the planet, and the Moon as, well, a moon Yes they do have a common centre of mass but it is inside the Earth - perhaps that could be a crucial point?

What ever this is (and I'd argue that it can could classed as science, as it's sort of developing a more rigorous classification system for objects in the universe) I think it's one of the most exciting things to happen with the Solar System since, well, the discovery of Pluto probably.

I can't wait to see the out come....plus I think I'm wanting to keep Pluto as a planet now and bring in loads of other objects. It really will lead to many more people being educated about other objects in the soalr system. So many people will never of heard of Ceres or Charon before.

Also, great to see you looking ahead to commercial space tourism and travel between stars

That said, density is even more important, as the moon is a hell of a lot more dense than a lump of ice.