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Author Topic: pluto not a planet?  (Read 16787 times)

Offline Soul Surfer

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Re: pluto not a planet?
« Reply #25 on: 30/08/2006 08:25:54 »
I and I believe most astronomers agree that a planet is a body orbiting a star that is big enough to clear all smaller debris from its orbital area.  The planets from Mercury to Neptune have done this. The minor planets between Mars and Jupiter are not big enough to do this although it is likely that they were a few larger bodies at one time that eventually collided and broke into bits.

Pluto is just a member of a whole group of similar minor planets mostly outside the orbit of neptune but is rather special in that it is strongly associated with Neptune and in an orbit in resonance with it and so could be considered as a possible "lost moon" of neptune

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Offline bostjan

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Re: pluto not a planet?
« Reply #26 on: 30/08/2006 11:02:38 »
What about debris that orbits in the Lagrange points of the "planet?"  Is there a special case to exclude them?  Otherwise, nothing would be a planet, as Alan Stern pointed out.

This is a very valid point that needs to be addressed.

I am unhappy with any definition that deals with the existance of debris or not, since it cannot be determined that there is no debris.
 

Offline Soul Surfer

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Re: pluto not a planet?
« Reply #27 on: 30/08/2006 12:59:09 »
You are being pedantic.  Obviously there are smaller objects orbiting in similar and crossing orbits to a planet by debris I mean major objects  of similar size to the "planet" orbiting in a very similar orbit.

It is quite possible to have many minor planet sized objects orbiting together  in similar orbits and have them stable for many thousands of millions of years but one object the size of the earth would have a strong enough gravitiational field either to crash into them or eject them from the area quite quickly  so a planet is  a lump that is big enough to have some control over its local environment.



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Offline bostjan

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Re: pluto not a planet?
« Reply #28 on: 31/08/2006 04:45:32 »
so is the definition of a plent to be, from now on, a body orbiting a star with a mass small enough not to be able to fuse hydrogen, yet big enough to be rounded by it's own gravity and that it must be the largest object in it's orbital path?  from what i've read in the news, and online, they never mentioned that objects cleared had too be of similar size.
 

Offline bostjan

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Re: pluto not a planet?
« Reply #29 on: 30/08/2006 05:40:36 »
yeah, but just pick up an old (early 1990's or before) astronomy book and look up "planet," and you'll see what i mean.  a planet used to be any solid object revolving around the sun.  this definition was fine with me.  planets were further divided into major planets and minor planets.  this was rather pointless, since the older books defined the major planets by naming and listing them and saying that anything else was a minor planet.  perhaps all of my textbooks came from the same messed-up source, though.  who knows, but the argument is semantic.
 

Offline Soul Surfer

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Re: pluto not a planet?
« Reply #30 on: 30/08/2006 08:25:54 »
I and I believe most astronomers agree that a planet is a body orbiting a star that is big enough to clear all smaller debris from its orbital area.  The planets from Mercury to Neptune have done this. The minor planets between Mars and Jupiter are not big enough to do this although it is likely that they were a few larger bodies at one time that eventually collided and broke into bits.

Pluto is just a member of a whole group of similar minor planets mostly outside the orbit of neptune but is rather special in that it is strongly associated with Neptune and in an orbit in resonance with it and so could be considered as a possible "lost moon" of neptune

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Offline bostjan

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Re: pluto not a planet?
« Reply #31 on: 30/08/2006 11:02:38 »
What about debris that orbits in the Lagrange points of the "planet?"  Is there a special case to exclude them?  Otherwise, nothing would be a planet, as Alan Stern pointed out.

This is a very valid point that needs to be addressed.

I am unhappy with any definition that deals with the existance of debris or not, since it cannot be determined that there is no debris.
 

Offline Soul Surfer

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Re: pluto not a planet?
« Reply #32 on: 30/08/2006 12:59:09 »
You are being pedantic.  Obviously there are smaller objects orbiting in similar and crossing orbits to a planet by debris I mean major objects  of similar size to the "planet" orbiting in a very similar orbit.

It is quite possible to have many minor planet sized objects orbiting together  in similar orbits and have them stable for many thousands of millions of years but one object the size of the earth would have a strong enough gravitiational field either to crash into them or eject them from the area quite quickly  so a planet is  a lump that is big enough to have some control over its local environment.



Learn, create, test and tell
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Offline bostjan

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Re: pluto not a planet?
« Reply #33 on: 31/08/2006 04:45:32 »
so is the definition of a plent to be, from now on, a body orbiting a star with a mass small enough not to be able to fuse hydrogen, yet big enough to be rounded by it's own gravity and that it must be the largest object in it's orbital path?  from what i've read in the news, and online, they never mentioned that objects cleared had too be of similar size.
 

Offline neilep

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Re: pluto not a planet?
« Reply #34 on: 05/09/2006 17:51:12 »
I really think they should send Pluto a certificate or something and make it an honorary planet...after all..it's been generally accepted as one for a long time.
...akin to an honorary degree !

I'll deliver it..I'm good at holding my breath !!

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Re: pluto not a planet?
« Reply #34 on: 05/09/2006 17:51:12 »

 

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