Neptune shouldn't be a planet by IAU... - Page 2

Kristophe · #31 (**permalink**) 28-August-2006, 12:35 AM

I still say the "absurd number of planets" argument is as much bunk as one can get. It's like saying that humans should get their own class because there are too many mammals. Hell, let's give us a whole new kingdom. There are already too many animals to count.

JeDi · #32 (**permalink**) 28-August-2006, 12:45 AM

[Mike Brown explains orbital dominance]

Quote:

Originally Posted by Ara Pacis

When I read through that page by Mike Brown, I see some wording that makes me think that he is not entirely happy with the result of the vote. On the surface he comes across as supportive, but reading between the lines I sense otherwise.

You will get a clearer picture if you, instead of trying to read between the lines, read the lines Brown actually wrote over the past years, weeks, days. To summarize:

- Some years ago he advocated the criterion of orbital dominance.

- About one year ago he changed to the cultural definition, found here in section "Is this object really a planet? Is Pluto a planet? What makes a planet?".

- He opposed the Gingerich proposal since when it was out.

- He supported the Fernandez proposal since when it was out.

I hadn't (and still haven't) any doubt that, although he might have preferred the "cultural definition" for the public (I don't imply egoism here), he honestly considers the resulting resolution as scientifically sound and still better for public use than the initial proposal.

There is presumably some disappointment about 2003UB313 not becoming the 10th planet (see the Requiem for Xena) and some relief about the whole uncertainty about its status, naming rules etc. being finally over. And as a teaching Professor of Planetary Astronomy he has to face some (positive) changes too. Maybe all this makes him somewhat itchy, his emotional state not yet completely settled, I don't know. But many people have to reorder their "astronomical cortex" today.

JeDi · #33 (**permalink**) 28-August-2006, 12:52 AM

Quote:

Originally Posted by Kullat Nunu

Well, I guess no one is absolutely happy with the outcome,

I still wonder how this wording was hammered together.

Quote:

although the definition itself no doubt has lots of supporters (including me, if that counts). The resolution text itself is just plain horrible and requires too much explaining.

Essentially you have to know where it comes from to know what it is supposed to mean.

Quote:

I think Mike Brown isn't happy because he haven't discovered a new planet, but as a scientists he very well know that accepting Pluto and 2003 UB313 could lead to an absurd¹ situation of a too large number of planets.

Not if you accept Pluto and 2003UB313 - but nothing else …

Ara Pacis · #34 (**permalink**) 28-August-2006, 01:16 AM

Quote:

Originally Posted by JeDi

[Mike Brown explains orbital dominance]

You will get a clearer picture if you, instead of trying to read between the lines, read the lines Brown actually wrote over the past years, weeks, days. To summarize:

- Some years ago he advocated the criterion of orbital dominance.

- About one year ago he changed to the cultural definition, found here in section "Is this object really a planet? Is Pluto a planet? What makes a planet?".

- He opposed the Gingerich proposal since when it was out.

- He supported the Fernandez proposal since when it was out.

I hadn't (and still haven't) any doubt that, although he might have preferred the "cultural definition" for the public (I don't imply egoism here), he honestly considers the resulting resolution as scientifically sound and still better for public use than the initial proposal.

There is presumably some disappointment about 2003UB313 not becoming the 10th planet (see the Requiem for Xena) and some relief about the whole uncertainty about its status, naming rules etc. being finally over. And as a teaching Professor of Planetary Astronomy he has to face some (positive) changes too. Maybe all this makes him somewhat itchy, his emotional state not yet completely settled, I don't know. But many people have to reorder their "astronomical cortex" today.

Interesting point, but not sure why you quoted me. I'm no longer saying he is against it, only that he is unhappy with it.

JeDi · #35 (**permalink**) 28-August-2006, 04:29 PM

Quote:

Originally Posted by Ara Pacis

Interesting point, but not sure why you quoted me.

Because you tried to read between the lines despite the lines providing much more insight themselves. And it was addressed at you, in the first place, and a quote is a good hint at whom I'm talking to.

Quote:

I'm no longer saying he is against it, only that he is unhappy with it.

Quote:

On the surface he comes across as supportive, but reading between the lines I sense otherwise.

"Otherwise" could also mean "not supportive," and I don't see this. Some discomfort is probably there, a part related to the general problem of a scientific definition and another part of a more sentimental kind (requiem).

jfribrg · #36 (**permalink**) 28-August-2006, 04:45 PM

As was predicted on this board a few months ago, the IAU definition satisfies nobody and doesn't end the debate. Anyway, it's nice to see mainstream coverage of an astronomical issue that doesn't involve planetary alignments, pole shifts or comet-trailing spaceships. Granted, arguing semantics is only a small step in the right direction, but it's a start. My definition is that its a planet if I think it is a planet. Overall, I think the IAU definition is good.

Some day we will find an object that blurs the line between planet and "not a planet". If Instead of 98%, an object is found that has cleared say 71% of the mass in its vicinity, then what? I also wonder why the entire Kuiper seems to be lumped into the same "vicinity". The Kuiper belt is a volume that dwarfs the volume occupied by the inner planets. Isn't it possible that there are different regions of this volume occupied by planets?

baric · #37 (**permalink**) 28-August-2006, 05:12 PM

Quote:

Originally Posted by jfribrg

As was predicted on this board a few months ago, the IAU definition satisfies nobody and doesn't end the debate.

This is not true. I, as well as many others on this forum, were proponents of an orbital dominance scheme to define planets. I think that the wording was perhaps more hastily-written than I would have liked, but I am greatly satisfied with the intent of the decision.

And, in fact, I suggested the term "dwarf planets" over a week ago for the small, Pluto-like planets that were not orbitally dominant. So I'm very satisfied!

Quote:

Anyway, it's nice to see mainstream coverage of an astronomical issue that doesn't involve planetary alignments, pole shifts or comet-trailing spaceships. Granted, arguing semantics is only a small step in the right direction, but it's a start. My definition is that its a planet if I think it is a planet. Overall, I think the IAU definition is good.

I agree whole-heartedly.

Quote:

Some day we will find an object that blurs the line between planet and "not a planet". If Instead of 98%, an object is found that has cleared say 71% of the mass in its vicinity, then what? I also wonder why the entire Kuiper seems to be lumped into the same "vicinity". The Kuiper belt is a volume that dwarfs the volume occupied by the inner planets. Isn't it possible that there are different regions of this volume occupied by planets?

You know, I wonder if 71% is really possible in the long run. The nature of gravity is such that a orbiting body should reach a critical, runaway point where it rapidly consumes (or ejects) the smaller bodies in its orbital region. This could be why the planet-moon mass is so extreme for systems with naturally-evolved moons (as opposed to impact-created moons like Luna and Charon).

It's also possible that the weak 40% dominance managed by Ceres could be near the upper end before reaching this runaway point. After all, it's widely accepted that the asteroid belt has not formed into a planet because of the effect of Jupiter. If Jupiter were not so massive, then perhaps Ceres would have already cleared out it's orbital region.

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