Planetary classification

On Mar 20, 9:36 am, Andrew Usher wrote:
Some time ago I came across this page
(http://arcbuilder.home.bresnan.net/PCLMaster.html) (I don't remember
how) and was quite interested. Though unfortunately we have only our
own solar system to study right now, contemplating the other
possiblities is certainly worthwhile.

I had once imagined making such a list myself, but was not confident
of my knowledge.

As I was reading it, I found many apparent inaccuracies

FYI : The 'Meghar' Scale is now the defacto standard in planetary mass
classification. There is something there for everybody :

http://groups.google.com/group/sci.a...5d5976374dc39a

I've filled in the 'Lunar' class, and added a 'Enceladas' class of ice
moons, and thus it now extends from the minimum spheroidal planet all
the way up into the brown dwarf and dwarf star regime, due to a
fortuitous set of solar system circumstances with respect to Jupiter
and solar masses :

http://en.wikipedia.org/wiki/List_of...bjects_by_mass

http://en.wikipedia.org/wiki/Image:G...e_masses_2.png

The original blog post I did on this is offline, but I will eventually
get around to reblogging it on my latest science blog :

http://konstantin-tsiolkovsky.blogspot.com/

The credit for this goes to Willie Meghar, all I did was polish it up
and present it to the scientific community, where it was immediately
embraced by most of the hard core participants in this 'debate'.

On Mar 20, 10:10 am, kT wrote:

FYI : The 'Meghar' Scale is now the defacto standard in planetary mass
classification. There is something there for everybody :

http://groups.google.com/group/sci.a...5d5976374dc39a

Well, I'm not sure how accepted this is, I find rather few hits for
'Meghar scale'.

Anyway, I couldn't endorse this as a primary classification system.
The most important
characteristic of a planets is its composition, not its mass. Grouping
together a 10 Me
'super-Earth' and an equal-mass giant is hardly helpful. Certainly, a
division entirely based
on factors of 10 is unreasonable here; if we do want to use arbitrary
mass thresholds (which
we shouldn't) they should be based on physical differences: for
example, the minimum mass
(on average) to attain hydrostatic equilibrium, the minimum to retain
an atmosphere, etc.

Note that _any_ system will have some borderline cases; that's the
nature of classification.
Groups based on mass, like the 'Meghar scale', don't really solve the
problem, they just
ignore it.

The credit for this goes to Willie Meghar, all I did was polish it up
and present it to the scientific community, where it was immediately
embraced by most of the hard core participants in this 'debate'.

Where may I find this 'debate'? I'd like to know what others have
thought, of course.

Andrew Usher

On Mar 21, 8:54 am, Andrew Usher wrote:
On Mar 20, 10:10 am, kT wrote:

FYI : The 'Meghar' Scale is now the defacto standard in planetary mass
classification. There is something there for everybody :

http://groups.google.com/group/sci.a...5d5976374dc39a

Well, I'm not sure how accepted this is, I find rather few hits for
'Meghar scale'.

Don't worry, it's been thoroughly discussed.

Anyway, I couldn't endorse this as a primary classification system.
The most important
characteristic of a planets is its composition, not its mass.

That's true, but composition is entirely different and much more
complex, the Meghar scale is a mass scale, and thus straightforward,
especially in an era where our knowledge of exoplanets is still
primitive, and mass and orbit are the only really clear data we have
at this point. A compositional scale is an entirely different scale,
and I encourage you to develop one, but right now the Meghar scale is
the best one out there for describing the masses and sizes of planets
with our solar system as the reference point, and it is far more
descriptive and exoplanet friendly than the crap that came out of the
IAU in the last few years. That is really a black mark on the IAU that
isn't going away.

Grouping
together a 10 Me
'super-Earth' and an equal-mass giant is hardly helpful. Certainly, a
division entirely based
on factors of 10 is unreasonable here; if we do want to use arbitrary
mass thresholds (which
we shouldn't) they should be based on physical differences: for
example, the minimum mass
(on average) to attain hydrostatic equilibrium, the minimum to retain
an atmosphere, etc.

You have to make an arbitrary decision of your breakpoints in any
scale, this scale happens to coincide remarkably with OUR solar
system. We even have an example of a planet that straddles adjacent
scales : Mercury, roughly halfway between a lunar class planet and a
Mars class planet (by mass).

Note that _any_ system will have some borderline cases; that's the
nature of classification.

i.e. - Mercury.

Groups based on mass, like the 'Meghar scale', don't really solve the
problem, they just
ignore it.

It ignores everything except mass. We further refine and distinguish
super Earths and gas planets, gas giants, super giants, solid metal
death star planets, brown dwarfs, dwarf stars, etc. In this scheme,
'dwarf' is qualitative and descriptive, just because Ceres and Pluto
are dwarfs doesn't make them non-planets, just as dwarf humans are not
non-humans. The IAU really took their eye off the 'ball' on this one.

The credit for this goes to Willie Meghar, all I did was polish it up
and present it to the scientific community, where it was immediately
embraced by most of the hard core participants in this 'debate'.

Where may I find this 'debate'? I'd like to know what others have
thought, of course.

It was on my blog : http://cosmic.lifeform.org (which is now offline).

Just because you don't see the debate, doesn't mean it didn't happen,
just as if you don't see planets, doesn't mean they don't exist.

Next up : moons of exoplanets and bizarre starlike objects.

Well, I'm not sure how accepted this is, I find rather few hits for
'Meghar scale'.

Don't worry, it's been thoroughly discussed.


If you're implying that everyone interested agrees that this is the
right way
to classify planets, I'm not persuaded.

Anyway, I couldn't endorse this as a primary classification system.
The most important
characteristic of a planets is its composition, not its mass.

That's true, but composition is entirely different and much more
complex, the Meghar scale is a mass scale, and thus straightforward,
especially in an era where our knowledge of exoplanets is still
primitive, and mass and orbit are the only really clear data we have
at this point.

That doesn't imply it's useful. We already know the mass, and we
already
use (for exoplanets) common terms to describe the mass range, so what
purpose is there in making this a formal scale? You haven't answered
that.

A compositional scale is an entirely different scale,
and I encourage you to develop one, but right now the Meghar scale is
the best one out there for describing the masses and sizes of planets
with our solar system as the reference point, and it is far more
descriptive and exoplanet friendly than the crap that came out of the
IAU in the last few years. That is really a black mark on the IAU that
isn't going away.


I don't know why you have a problem with the IAU decision, assuming
you mean the definition of 'planet'. It's a non-arbitrary definition
that will
clearly be applicable to other solar systems as well. The 'Meghar
scale'
is not such.

Grouping together a 10 Me
'super-Earth' and an equal-mass giant is hardly helpful. Certainly, a
division entirely based
on factors of 10 is unreasonable here; if we do want to use arbitrary
mass thresholds (which
we shouldn't) they should be based on physical differences: for
example, the minimum mass
(on average) to attain hydrostatic equilibrium, the minimum to retain
an atmosphere, etc.

You have to make an arbitrary decision of your breakpoints in any
scale, this scale happens to coincide remarkably with OUR solar
system.

That is not a merit, given that the system should apply to all planets
in
the universe.

Groups based on mass, like the 'Meghar scale', don't really solve the
problem, they just
ignore it.

It ignores everything except mass. We further refine and distinguish
super Earths and gas planets, gas giants, super giants, solid metal
death star planets, brown dwarfs, dwarf stars, etc.

So, this proposes that the top-level classification should be mass,
with
further distinctions lower down. This is almost as ridiculous as an
analogous classification of animals first on size.

In this scheme,
'dwarf' is qualitative and descriptive, just because Ceres and Pluto
are dwarfs doesn't make them non-planets, just as dwarf humans are not
non-humans. The IAU really took their eye off the 'ball' on this one.

Just because you don't see the debate, doesn't mean it didn't happen,
just as if you don't see planets, doesn't mean they don't exist.

I'm not sure what you're trying to get across here.

Andrew Usher

On Mon, 24 Mar 2008 05:29:35 -0700 (PDT), in a place far, far away,
Andrew Usher made the phosphor on my monitor
glow in such a way as to indicate that:


Well, I'm not sure how accepted this is, I find rather few hits for
'Meghar scale'.

Don't worry, it's been thoroughly discussed.


If you're implying that everyone interested agrees that this is the
right way
to classify planets, I'm not persuaded.

Bear in mind that you're discoursing with the most notorious troll in
this newsgroup (sci.space.policy).

On Mar 24, 6:29 am, Andrew Usher wrote:
Well, I'm not sure how accepted this is, I find rather few hits for
'Meghar scale'.

Don't worry, it's been thoroughly discussed.

If you're implying that everyone interested agrees that this is the
right way
to classify planets, I'm not persuaded.

So what. It's the right way to classify exoplanets with respect to our
own planets, because the orders of decimal magnitude match up almost
perfectly (with the exception of Mercury) with our planets, and we
can't yet see any exoplanets in any detail, we can only speculate.

Anyway, I couldn't endorse this as a primary classification system.
The most important
characteristic of a planets is its composition, not its mass.

That's true, but composition is entirely different and much more
complex, the Meghar scale is a mass scale, and thus straightforward,
especially in an era where our knowledge of exoplanets is still
primitive, and mass and orbit are the only really clear data we have
at this point.

That doesn't imply it's useful. We already know the mass, and we
already
use (for exoplanets) common terms to describe the mass range, so what
purpose is there in making this a formal scale? You haven't answered
that.

Because of the FORTUITOUS and REMARKABLE lineup of the decimal scales
of magnitude with our own solar system, I've already described it to
you, given you the necessary links so that you can see it for
yourself, and anybody interested has already discussed this in great
detail. Planetary composition is extremly complex and for the most
part unknown, for instance :

http://planetary.org/image/interior_...comparison.png

There is no method of easy classification of planetary composition of
structure, any analysis is decades off for exoplanets, but mass is
trivial, and I have presented an extremely succinct method of
expressing it in terms of solar system bodies, which presents a whole
new spectrum of exoplanet masses that we are sure to discover in the
future.

A compositional scale is an entirely different scale,
and I encourage you to develop one, but right now the Meghar scale is
the best one out there for describing the masses and sizes of planets
with our solar system as the reference point, and it is far more
descriptive and exoplanet friendly than the crap that came out of the
IAU in the last few years. That is really a black mark on the IAU that
isn't going away.

I don't know why you have a problem with the IAU decision, assuming
you mean the definition of 'planet'. It's a non-arbitrary definition
that will
clearly be applicable to other solar systems as well. The 'Meghar
scale'
is not such.

It most certainly is. Just because you claim something isn't so,
doesn't make it not so. You have to provide supporting evidence,
something I have done in great quantities here in this discussion.

Grouping together a 10 Me
'super-Earth' and an equal-mass giant is hardly helpful. Certainly, a
division entirely based
on factors of 10 is unreasonable here; if we do want to use arbitrary
mass thresholds (which
we shouldn't) they should be based on physical differences: for
example, the minimum mass
(on average) to attain hydrostatic equilibrium, the minimum to retain
an atmosphere, etc.

You have to make an arbitrary decision of your breakpoints in any
scale, this scale happens to coincide remarkably with OUR solar
system.

That is not a merit, given that the system should apply to all planets
in
the universe.

Good luck with that. Mass happens to be universal, if you haven't
noticed that yet.

Groups based on mass, like the 'Meghar scale', don't really solve the
problem, they just
ignore it.

It ignores everything except mass. We further refine and distinguish
super Earths and gas planets, gas giants, super giants, solid metal
death star planets, brown dwarfs, dwarf stars, etc.

So, this proposes that the top-level classification should be mass,
with
further distinctions lower down. This is almost as ridiculous as an
analogous classification of animals first on size.

Animals that we can't see, probably won't be able to see for decades.

I think I'll go with the Meghar scale for the near future.

It's now. I need it and use it right now.

In this scheme,
'dwarf' is qualitative and descriptive, just because Ceres and Pluto
are dwarfs doesn't make them non-planets, just as dwarf humans are not
non-humans. The IAU really took their eye off the 'ball' on this one.

Just because you don't see the debate, doesn't mean it didn't happen,
just as if you don't see planets, doesn't mean they don't exist.

I'm not sure what you're trying to get across here.

You, on the other hand, are coming through loud and clear.

You're an idiot.