Should Pluto remain a planet?

[Theodoric]

To help the International Astronomical Union in its current deliberations on the status of Pluto I thought that we could help them out by conducting our own little poll. I'm sure that the mods could forward the results - somewhere in Prague, isn't it?

Personally, I go for demoting it, if only for the amusement of watching the astrologers trying to explain it away.

[Graham M]

I think it should be divided up like it is in Star Trek - IE M Class for Breathable Atmosphere, etc.

[greencreeper]

A global AIDS problem. A global obesity problem. We're fighting the 3rd World War. The Middle East is in tatters. But no - lets discuss a cold bit of rock we'll never see, let alone visit.

[AntiSilence]

Always the way lol

[Anonymouse]

Mmm...debatable.

There's a possibility that it was pure coincidence that Pluto was very close to where astronomers predicted there was, or should be, a ninth planet. The prediction was made on the basis of the observed perturbations in Neptune's orbit - in fact, Neptune was discovered in exactly the same manner, i.e. the perturbations in the orbit of Uranus. But Pluto has nowhere near the required mass to affect Neptune's orbit to the observed extent, even allowing for its tiny moon, Charon. Both together aren't even as massive as our Moon.

With the much more accurate mass measurements from the Voyager probes, virtually all the perturbations can now be accounted for, which pretty much disposes of the notion of a large, extremely massive planet further out than Pluto.

If you define a planet as a body of a certain size and/or mass that orbits the Sun, then whether Pluto is a planet or not depends on where you draw the line re size and/or mass. If on the other hand you define a planet merely as a body (not a comet or asteroid) which orbits the Sun, then there are rather more than just 9 planets here. There's all sorts of cosmic junk left over from the formation of the solar system, apart from the Asteroids.

[Shaun]

Originally Posted by Anonymouse

even allowing for its tiny moon, Charon. Both together aren't even as massive as our Moon.

Tiny?

Due to the unusual similarity in size between Charon and Pluto, they are sometimes considered a double planet.

[greencreeper]

Charon Bit of a strange name for a moon.

[Cobbydaler]

Pluto was the god of wealth & ruler of the underworld in greek mythology...

Charon was the ferryman across the river aceron who carried the dead into hades...

[Cobbydaler]

Originally Posted by Aragorn

It looks like Pluto is going to learn it's fate quite soon - BBC report

Looks like it may have been reprieved, and a few more planets added...

A planet has to be round apparently!!

ADMIN EDIT (Chris T): Moved from the Planet Sizes thread.

I have removed a huge pile of off-topic nonsense from this thread. Can we please try to remember this is a topic-based discussion forum, not an AOL chatroom.



---------- Post added at 12:16 ---------- Previous post was at 11:49 ----------

And now a second round of deletions. Come on, people.

How about a planet orbits a star
a moon orbits a planet

Major Classes of moon/planet

Alpha: A planet/Moon where life however primative exists whether native or planted

Beta: A planet/moon with Liquid ocean(s) or atmosphere
greater than 1 millibar.

Gamma: A planet/moon with a frozen atmosphere or frozen ocean.

Delta: A rocky planet/moon (e.g Mercury) Dia greater than 1000KM


Epsilon: reserved

Minor Planet/moons:-

Zeta: Moon/Planet
100-1000Km Dia if volume transformed to a sphere

Eta: Moon/Planet
10-100Km Dia if vol etc

Theta: as above but 1-10 KM

Iota: less than 1KM



Kappa: Size/compostion indeterminate

Lambda to omega classes reserved.

Each class could have sub-divisions E.G. A1, A2 etc

THis system would allow for the fact that moons can have atmospheres and life
leave yet other types of undiscovered planets to be classified

[Theodoric]

Originally Posted by Cobbydaler

Looks like it may have been reprieved, and a few more planets added...

A planet has to be round apparently!!

ADMIN EDIT (Chris T): Moved from the Planet Sizes thread.

Roundness is as good a criterion as any. It means that the celestial body is massive enough for gravity to force it into a spherical shape. It thus gets round the problem of the density in that a large diameter low density planet can be equivalent to a low diameter high density planet.

[andygrif]

Well I'm more confused now, not being an expert on such things. Listen to radio news headlines yesterday morning, they said Pluto was a planet. Watching the news headlines last night, they said it had been 'downgraded' to a Pluton (which sounds like an inhabitant to Pluto to me) and looking at the IAU website it's both!

Anyway, for those just as confused as me, there's a FAQ here

http://www.iau2006.org/mirror/www.ia...u0601_Q_A.html

Originally Posted by Theodoric

Roundness is as good a criterion as any. It means that the celestial body is massive enough for gravity to force it into a spherical shape. It thus gets round the problem of the density in that a large diameter low density planet can be equivalent to a low diameter high density planet.

Hmmm Not sure I'd use roundness, that could be as small as a single drop of liquid in space. I'd just say the equivalent sphere from the current volume. - we could one day find a massive chunk of iron thrown out from a colossal star so massive as to have an atmosphere and life but not necessarily even remotely spherical. Who know's what's out there yet to be discovered.. (strains of the twiglet zone in the background).

Pluto should remain a planet otherwise we'll all have to fork out for yet another set of 'up to date' books for the school.

[little monster]

I really do not understand what it matters.

Oh my, they found out that some object orbiting the sun doesn't meet the criteria for being ap lanet after all. Oh no, the world is coming to an end unless we resolve this problem ...

Pragmaticially, a "planet" should be defined as something that does encompass all the original planets, though - but i dont think this is the least bit important.