[meteorite-list] 'Plutons' Push Planet Total Up To 12

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Wed Aug 16 16:14:55 2006
Message-ID: <8nt6e2dk0itt7m80ljbelasklb664op0tl_at_4ax.com>

On Wed, 16 Aug 2006 11:25:52 -0700, you wrote:

>Hi Darren:

>What happens when you find something that is say the size of the Moon or just a
>little smaller than Mercury at the outer edges of the Kuiper Belt. This is not
>out of the question. What do you call it then? Just say too bad we have 9 (or 8
>planets)

I'm sure that we will find more and larger KBOs out there-- that is part of the
problem-- do you want a list of 30 planets in the solar system? Or 40? And it
cuts both ways-- what if you find a KBO just slightly smaller than the KBOs that
are concidered planets-- say, it is 5 percent too small to become spherical due
to it's own gravity, but is otherwise compositionally identical to ones that are
slightly bigger. Is it a planet, or not? If not, isn't the cut-off of
"spherical" pretty arbitrary?

There is a commercial that airs currently on the US "PBS" system-- I honestly
can't say I paid close enough attention to what programming it is advertising
and hopefully someone else here who watches PBS can clear this up, but it
involves a man who has some position in new science programming on PBS. He is
walking through the streets of a city and random people on the street are
greeting him and asking him science questions. One of those people asks him if
Pluto is a planet-- he replied (paraphrasing here) that if Pluto was brought to
the distance of Earth, it would have a tail-- "that's not the behavoir of a
planet". That's pretty much what sticks with me-- if you brought a KBO into the
inner solar system, it probably wouldn't act like a planet, it'd act like a
really big comet and boil largely away.

>Saying that this is just the "opinion" of a group of astronomers shows a
>disrespect for astronomy as a science. Yes, you can have your own opinion.
>However, a lot of time and thought and research went into this proposal. It is
>more than just an opinion. It is solidly based on observation and the physical
>nature of the objects in our Solar System and other objects that are likely to
>be found in the future. Is is perfect? Probably not. But it is necessary.

It is based "on observation and the physical nature of objects in the solar
system" that objects of a certain size collapse into a spherical shape due to
their own gravity, yes, absolutely. What is opinion, though, is that the word
"planet", which is an ancient word that predates science as we know it, should
be now officially redefined to mean "an object that orbits the sun and is big
enough to form a sphere under it's own gravity". If the public wants to accept
that newly coined by committee definition of an ancient word, they are free to
do so. But if they want to reject it, they are free to do that, too.

Remember, a name isn't something fundamental-- it is just a label stuck on
something to make it convenient to talk about it, rather than point and grunt.
I just think that it is more convenient to limit the name "planet" to the 4
terrestrial and 4 jovan planets than include a smorgasbord of small bits of
debris. And if really pushed on it, judging from what we've seen of other solar
systems so far with the limited tools at hand, I'd have to say that the jovans
are the real planets while the terrestials are just larger than average bits of
stony debris left over from forming the 4 planets. :-) But I wouldn't go that
far.
Received on Wed 16 Aug 2006 04:15:44 PM PDT