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Should Pluto be classed a planet?

bunthulhu

But is this not due to the fact that it is orbiting the Earth, which also ends up in the same place?

But I point you back to the point I made about them technically orbiting each other.... :wink:

Ah okay, I didn't realise they'd spotted one yet, that's interesting :smile:

So basically it is correct to classify them as stars? I wonder if there is one in the Oort Cloud after all, as one theory goes :smile:

Not heard of that theory before...my brown dwarf knowledge is quite limited. Is one being there supposed to explain some strange gravitational effect we see in the Solar System but which we cannot expalin yet?

Hmmm, I agree this situation would be unusual, but I think I would still classify the Earth as a moon if this were the case :p:

Besides, we wouldn't be here to argue about it if it were :biggrin:

I just wonder what the point of this would be :p:

It just seems a shame to throw away the wonderful definition of the 8 planets as they are, lying on the ecliptic with their mildly elliptical orbits and their lovely inner-outer planet pattern :biggrin:

Now, don't get sentimental...if all scientists were like that in the past we'd still have the Earth ebing flat and electricity going the other way around a circuit.

No I don't actually, that's quite an interesting thought. I doubt it would be possible though, surely the third body would be drawn into the orbit of the first, largest body?

That is what I though, but if their masses were all similar, perhaps even if we had three identical bodies together (theoretically possible, if near impossible in practice), what would be the outcome? I wonder if anyone has ever tried to simulate such a thing on a computer. I'd be very interested in the results...

Reply 61

Mad Vlad

19

bunthulhu

But is this not due to the fact that it is orbiting the Earth, which also ends up in the same place?

No I don't actually, that's quite an interesting thought. I doubt it would be possible though, surely the third body would be drawn into the orbit of the first, largest body?

Indeed. If you drew a plot of the Moon was it travelled round the sun, you'd get something that resembles a spirograph drawing. The Moon only orbits the sun because it orbits the Earth, which orbits the Sun.

Trinary systems in theory could work, although, if there was 3 bodies of similar mass, their orbits would be unpredictable and would end in tears. However, if there was 1 massively larger object and 2 smaller, the 1 would take on the role of "planet" and the other 2 would be "moons" and would orbit the primary object. Although, you could say that Mars is a trinary system anyway.

Actually, wasn't a trinary system, or sorts, formed when the all the rockets wnt to the Moon? I know the rockets were tiny in comparison, but we had the rocket orbiting teh Moon and the Moon orbiting the Earth, meaning in principle such a system is possible, i created artificially in this situation.

Now the only question I have is if the rockets were in a stable orbit of the Moon or whether they needed to make serious corrections to their course in order to stay in orbit around the moon...if they hadn't, would the rockets have been automatially dragged back to the Earth?

Reply 63

Mad Vlad

19

Roger Kirk

Now the only question I have is if the rockets were in a stable orbit of the Moon or whether they needed to make serious corrections to their course in order to stay in orbit around the moon...if they hadn't, would the rockets have been automatially dragged back to the Earth?

Unlikely as the strength of the Earth's gravity on the rockets would have been almost zero, in fact, so small, you could probably discount it from any calculations. Conversely, the Moon's gravity would have been the dominant force and as such, corrections probably would not have had to have been made.

Reply 64

bunthulhu

14

Roger Kirk

But I point you back to the point I made about them technically orbiting each other.... :wink:

But the Earth is predominantly in orbit around the Sun, and anyway, the common centre of mass of the Earth-moon system is still within the Earth, surely rendering the Earth the superior body? :p:

Roger Kirk

Not heard of that theory before...my brown dwarf knowledge is quite limited. Is one being there supposed to explain some strange gravitational effect we see in the Solar System but which we cannot expalin yet?

Yes, it would explain what is hurling comets out of the Oort cloud towards us :smile:

Roger Kirk

Now, don't get sentimental...if all scientists were like that in the past we'd still have the Earth ebing flat and electricity going the other way around a circuit.

The difference is, those ideas were wrong :p:

I don't think my neat definition is wrong, I am just being stricter than most and trying not to complicate matters :smile:

Roger Kirk

That is what I though, but if their masses were all similar, perhaps even if we had three identical bodies together (theoretically possible, if near impossible in practice), what would be the outcome? I wonder if anyone has ever tried to simulate such a thing on a computer. I'd be very interested in the results...

I agree with Mad Vlad on this one, I think it would most probably end either in tears or in a planet-moon system. But then again who knows, my brain is too small to compute such things :biggrin:

Mad Vlad

Unlikely as the strength of the Earth's gravity on the rockets would have been almost zero, in fact, so small, you could probably discount it from any calculations. Conversely, the Moon's gravity would have been the dominant force and as such, corrections probably would not have had to have been made.

Thanks.

But even then, my example there is pretty pointless and I was talking about three large objects before, all of which could possible be described as planets if they were orbiting the Sun (individually)

Unless I'm grossly mistaken, the moon rockets cwere never anywhere near planetary size...lol :biggrin:

Reply 66

Onearmedbandit

17

I'm pretty sure it IS, and will always be, a planet. What will be changed is its type of planet.

Reply 67

nic88

2

so if pluto isn't classed as a planet anymore, what happens to "My Very Easy Method Just Speeds Up Naming Planets"???

Just remembered the fact that i learnt another one of these rhymes once. Something like "Many Vile Earthlings Munch Jam Sandwiches Under Newspaper Piles".

Much better than the first one in my opinion :biggrin:

Reply 68

SuperhansFavouriteAlsatian

Zakatu

I must say i'm surprised! So despite the logical inconsistancy (there are bigger objects than pluto not classed as planets) you still want Pluto to be a planet? if you do then does that mean you want those other objects to be planets.

Nope, i just don't give a ****. Who cares? I wonder how much all this beauracratic rubbish has cost, just to chose a name? Who frickin cares?!

What is probably going to stop the Earth-Moon system being designated a double planet system?

900 miles. That is all. Not a great deal is it?

Looking at the proposals for the new definition of 'planet' it looks like a secodnary condition that the barycentre of two bodies must lie out side both bodies means the Moon cannot be considerd a planet but remains a satellite :frown:

) The Earth-Moon barycentre lies approximately 900miles beneath the Earth's surface...not a great distance at all is it?

On the other point of what could become a planet, the asteriods Vesta, Pallas and Hygiea may be candidates and possible pluton planet are Sedna, Orcus, Quaoar and 2003 EL61. Interesting to say the least...

Reply 70

username24

About the orbital thing:

Imagine you were classifying objects in the solar system from scratch. Start with three objects:

Jupiter
Triton
Pluto

Now under the present definition, Jupiter and Pluto would be in the same category (both orbit the Sun), and Triton would be the outlier! But everything else that is known about the masses, densities, compositions and histories of these bodies tells us that Triton and Pluto belong in the same category.

This is how I would categorise planetary bodies
http://homepage.ntlworld.com/sfjcody2/planetarycatesmallb.png
(note: TNOs other than Pluto-Charon not shown on this diagram for reasons of clarity)

Reply 71

croissantfever

12

Actuually changed my mind, they should reclassify planets as ANYTHING orbiting the sun within the Kuiper belt that has a radius of greater than 1000miles. this does include titan. and i think the moon. they should count. when i become astronomer royal i'm gonna suggest this :biggrin:

Reply 72

bunthulhu

14

Roger Kirk

What is probably going to stop the Earth-Moon system being designated a double planet system?

900 miles. That is all. Not a great deal is it?

Looking at the proposals for the new definition of 'planet' it looks like a secodnary condition that the barycentre of two bodies must lie out side both bodies means the Moon cannot be considerd a planet but remains a satellite :frown:

) The Earth-Moon barycentre lies approximately 900miles beneath the Earth's surface...not a great distance at all is it?

On the other point of what could become a planet, the asteriods Vesta, Pallas and Hygiea may be candidates and possible pluton planet are Sedna, Orcus, Quaoar and 2003 EL61. Interesting to say the least...

Hehe, seeee it was a cruicial point! :p:

Reply 73

bunthulhu

14

lakeofcake

Actuually changed my mind, they should reclassify planets as ANYTHING orbiting the sun within the Kuiper belt that has a radius of greater than 1000miles. this does include titan. and i think the moon. they should count. when i become astronomer royal i'm gonna suggest this :biggrin:

Even though they are technically orbiting their respective planets, rather than the Sun?

Reply 74

Arminius

OP

14

lakeofcake

Actuually changed my mind, they should reclassify planets as ANYTHING orbiting the sun within the Kuiper belt that has a radius of greater than 1000miles. this does include titan. and i think the moon. they should count. when i become astronomer royal i'm gonna suggest this :biggrin:

"within the kuiper belt" assumes you know where the inner system it ends... i would say it ends at Nepture.. i.e the planets.

"greater than 1000 miles". I would say thats a bit arbitary. But i guess we have to draw the line somewhere.

The moon is NOT a planet. A "moon" orbits a planet.

Reply 75

username24

Roger Kirk

What is probably going to stop the Earth-Moon system being designated a double planet system?

900 miles. That is all. Not a great deal is it?

In several billion years the Earth's Moon will become a planet (under this definition) as it migrates further from the Earth and the barycentre of the system increases.

Reply 76

bunthulhu

14

username24

In several billion years the Earth's Moon will become a planet (under this definition) as it migrates further from the Earth and the barycentre of the system increases.

Also in several billion years, the Sun will die and obliterate both the Earth and Moon, solving our little problem :smile:

Reply 77

NViasko

Astronomers and Scientists should maintain its traditional sense of identity.

Reply 78

Mr @

1

It's officially a Pluton now!

bunthulhu

Even though they are technically orbiting their respective planets, rather than the Sun?

Why should we have the condition that a planet must orbit a star in the first place?

It seems rather strange to define an object based on what happens to be near it.

Compare it to stars...we don't define a star based upon what it is near or what it moves around. We define it based upon what the object itself is like, it's physical properties of size, shape, composition and the processes which go on inside it.

Maybe a similar definition of planet it needed very similar to what has been proposed, but basically defined to be:

an object which is large enough under it's gravity to be approximately spherical, but not massive enough for internal hydrogen fusion to begin.

Though that definition probably brings brown dwarfs down to be planets....but this is also something not addressed yet by the 'official' proposition either: it has no maximum mass yet for a planet in the definition.

Should Pluto be classed a planet?

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