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Date: 26 Aug 2006 18:22:27
From: Richard Jarnagin
Subject: Planet Definition Questions
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Under the new definition, one of the requirements for an object to be called
a planet is that it clean out it's orbit of other objects. But now it seems
we need to define "cleaned out". Cleaned out to what degree? What about
the time aspect? Don't we need to look at "cleaned out" with respect to the
age of the stellar system? I realize that most of the cleaning is going to
come early in the development of the system, but still, this "cleaned out"
relative to age seems a relevant consideration. This part of the new
definition seems problematic to me. Never mind trying to apply it to actual
observations of other stellar systems with current technology.
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Date: 26 Aug 2006 19:30:29
From: Richard Jarnagin
Subject: Re: Planet Definition Questions
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And then there's the consideration of the central star(s) and other bodies
in the system. Does it matter what influence these played in clearing the
orbit of the object of consideration, or is it just the clearing done by the
object itself? How do you distinguish between the two? If you say that all
that matters is that the "neighborhood" be cleared, then the intrinsic
characteristics of the object are no longer as important and you will
undoubtedly end up with objects of a given size and mass ending up planets
in one stellar system but not in another.
"Richard Jarnagin" <rjarnagin@peoplepc.com > wrote in message
news:Dj0Ig.14189$xp2.3956@newsread1.news.pas.earthlink.net...
> Under the new definition, one of the requirements for an object to be
called
> a planet is that it clean out it's orbit of other objects. But now it
seems
> we need to define "cleaned out". Cleaned out to what degree? What about
> the time aspect? Don't we need to look at "cleaned out" with respect to
the
> age of the stellar system? I realize that most of the cleaning is going
to
> come early in the development of the system, but still, this "cleaned out"
> relative to age seems a relevant consideration. This part of the new
> definition seems problematic to me. Never mind trying to apply it to
actual
> observations of other stellar systems with current technology.
>
>
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Date: 26 Aug 2006 23:50:32
From: Richard Jarnagin
Subject: Re: Planet Definition Questions
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"Richard Jarnagin" <rjarnagin@peoplepc.com > wrote in message
news:pj1Ig.10599$Qf.8195@newsread2.news.pas.earthlink.net...
If you say that all
> that matters is that the "neighborhood" be cleared, then the intrinsic
> characteristics of the object are no longer as important and you will
> undoubtedly end up with objects of a given size and mass ending up planets
> in one stellar system but not in another.
For that matter, I don't see anything in the physics that would preclude it
from happening within the SAME stellar system. You could end up with a less
massive object orbiting close in to the central star where the star itself
has cleared out the orbit being defined as a planet with a more massive
object orbiting much further out failing to qualify.
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Date: 26 Aug 2006 12:54:56
From: Kevin Heider
Subject: Re: Planet Definition Questions
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On Sat, 26 Aug 2006 19:30:29 GMT, "Richard Jarnagin"
<rjarnagin@peoplepc.com > wrote:
> you will undoubtedly end up with objects of a given size and mass ending up
>planets in one stellar system but not in another.
Possibly. In OUR solar system we already have two moons (Saturn's
Titan & Jupiter's Ganymede) that are larger than the Planet Mercury.
Definitions are hard define in an unpredictable universe. Thus, the
current definition of Planet is only for OUR system. Mankind will
expand on it further as our knowledge of exo-planets increases.
I'm just glad the universe doesn't revolve around Pluto. :-)
"Richard Jarnagin" <rjarnagin@peoplepc.com > wrote:
>Under the new definition, one of the requirements for an object to be
>called a planet is that it cleared out it's orbit of other objects.
Read the 22 page article on "What is a planet?" by Steven Soter at:
http://arxiv.org/abs/astro-ph/0608359
It comes down to what I generically call "Gravitational Dominance in
the region". But any time you reduce 22 pages to a couple of words,
uh, good luck.
-- Kevin Heider
West Coast Swing Photos at:
http://www.pbase.com/kheider
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