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Is Pluto a planet?


Smithysteve

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Space craft 'New Horizons' is closing in on Pluto. it's mid July rendezvous will be big news. It will again raise the question "Is Pluto a Planet?"

The for and against brigades will be banging their drums... Metaphors will abound...

Pluto is a Kuiper Belt Object, hundreds of other similar sized bodies have been found 'out there' too. Some may be even larger... Eris is almost the same size... Haumea is a third of Pluto's mass. Makemake is two thirds... Does this demote Pluto (and them) to dwarf planet status?

Pluto is small, it has a diameter of only 1400 miles, it's big enough for Gravity to shape it spherical, it orbits the sun, so is this enough to classify it a planet?

If the other Kuiper Belt Objects did not exist would poor Pluto still be a 'planet'?

What do you think?

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Yes, I think so.

It had been a planet for about 70 years until the larger Kuiper Belt objects were found. So if there were no large KB objects then I think it would have retained its status.

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My atlas states it's a planet, but then it is an old atlas, ha ha. :screwloose:  


 


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No. It has failed to clear its orbital path of all reasonable debris, one of the defining attributes of a planet.


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If the other Kuiper Belt Objects did not exist would poor Pluto still be a 'planet'?

What do you think?

I still say yes, since there is no debris to clear if the other Kuiper Belt objects did not exist.

The defining attributes were only agreed on after the full extent of the KB objects were known.

If answering the title of the thread, then Pluto is definitely not a planet since the new attributes were agreed.

I think that with the knowledge we now have about the solar system, Pluto is definitely not a planet. However, it has spent the bulk of its known existence satisfying the previous definition of a planet.

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A tricky one this, as the goal posts keep moving since it's discovery and is clearly still an emotive topic. 


I like the tee shirt which has " I am old enough to remember when Pluto was a planet", on it.


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Just depends which question you are answering.

Q. If the other Kuiper Belt Objects did not exist would poor Pluto still be a 'planet'?

A. Yes.

Q. Is Pluto a planet?

A. No.

:)

If the other KBOs did not exist, I don't think that anyone would have dreamed of changing Plutos status. The goalposts have been changed due to our changing knowledge of the solar system.

Since 2006 it has been known as Minor Planet 134340 Pluto, but the spent the previous 70 odd years firmly being a planet in the classical sense until the debates started following the discovery of the 27% more massive and similar sized Eris in 2003.

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When I was younger, yes, a long time ago :-), I remember the definition of a planet was virtually any object that orbited the sun...

Astronomers now say pluto is not a planet. Planetary scientists at it is, and they know better!

Just because we have found lots more similar Pluto sized objects, they fear the main eight planets will be demoted to something less, so goal posts are moved (Baz), they have altered the criteria.

We now have a clearer understanding of what our solar system is made up of and better ways to classify parts of the solar system have to evolve too. I get that... Our planet and the other 7 other main planets are just that, main class planets, Pluto and similar ilk are another class of planets, dwarf. How small a dwarf planet has to be to become an asteroid etc I am not sure

A rose by any other name would smell as sweet... Hey, a dwarf planet is still a planet!

If it looks like a duck, waddles like a duck, and quacks like a duck, there's a good chance it's a duck! ... Pluto looks like a planet, has moons like a planet, orbits like a planet, it's small so I guess you could call it a dwarf planet.

For now!

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Too many questions in the original post! I think Steve did that on purpose to generate some interest. :thumbsup:

Q. Is Pluto a planet?

A. No, in accordance with the new definition.

Q. Pluto is a Kuiper Belt Object, hundreds of other similar sized bodies have been found 'out there' too. Some may be even larger... Eris is almost the same size... Haumea is a third of Pluto's mass. Makemake is two thirds... Does this demote Pluto (and them) to dwarf planet status?

A. Yes, in accordance with the new definition.

Q. Pluto is small, it has a diameter of only 1400 miles, it's big enough for Gravity to shape it spherical, it orbits the sun, so is this enough to classify it a planet?

A. No, not according to the new definition.

Q. If the other Kuiper Belt Objects did not exist would poor Pluto still be a 'planet'?

A. Yes, there would be no new definition.

Q. What do you think?

A. Now that is a whole new ball game :)

Personally, I'm happy to move on and accept the new arguments that Pluto is a different class of planet. But some may want to keep the debate going either on EMS ( who - me? :) ) or after the New Horizons rendezvous sparks it all off again. :)

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That criteria for a planet to have cleared it's orbit is a poor one, it was disputed at the time -


 


"Earth, Mars, Jupiter and Neptune have also not fully cleared their orbital zones. Earth orbits with 10,000 near-Earth asteroids. Jupiter, meanwhile, is accompanied by 100,000 Trojan asteroids on its orbital path."


 


http://news.bbc.co.uk/1/hi/sci/tech/5283956.stm


 


It's a difficult one to answer. If you were to reinstate Pluto as a planet, you'd really have to also promote Ceres.


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  • 1 month later...

Be it classified as one or not, to me its still that so far away cold lonely little planet that it was in my mind when I were young and first amazed at our solar system,galaxy and universe :)

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It has 5 moons doesn't it? It also is a similar size to other dwarf planets like ceres?

I've read the criteria for classification of a planet, but my take would be that it is too far away from the sun for its size to be considered a planet.

A size, orbit to distance ratio should be employed.....

It is a bit of a odd one out in that the small planet perhaps shares more similarities with inner planets over the larger gas giants.....

In short, I have no idea haha

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I thought this was interesting.   http://www.space.com/860-finding-pluto-tough-task-75-years.html    Dating from 2005.


 


Personally I think it should have been left as a planet simply because of the difficulty of finding it at that time. IMHO it has a historic right. I know that's subjective but ...........


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Who gets to decide on this anyways?

Is one guy like flipping a coin or something lol

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  • 2 weeks later...

To me, it is the ninth planet, for future generations, your kids etc, maybe not! Never say never though, after all the fuss that new horizons is making...

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I doubt it is going to be reinstated, due to the fact they have found objects in the Kuiper Belt that are a similar size or bigger than Pluto, meaning we will have thousands of planets in the solar system if they reinstate Pluto.

It was decided it was a planet based on currant information back in the 50's but as we know in science, things change and it is now classed a dwarf planet based on current understandings.

Edited by Daz Type-R
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Pluto will always have a special place in our hearts I suppose being taught at school it was the 9th planet kind of reinforces this. I like to think of it as a planet.

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