Vegman
It is not an asteroid. Many astronomers argue that being a sphere and
having a moon makes it a planet. Many other astronomers, like me,
don't want to call it a planet anymore and want some new word for it.
http://michele.gcccd.cc.ca.us/~ljohnson/johnson.html
Pluto is cataloged as one of the solar systems planets. It is a binary
system with a companion called Charon (Pronounced care-ron.)
Some physical data on Pluto:
Mass: 0.0018 Earth Masses
Radius: 1140 Km at the equator. (Spherical shape.)
Average Distance from sun: 39.44 Au
Sidereal period. 248.6 years.
Rotation rate: 6.439 days.
Data on Charon:
Distance from Pluto (center of planet): 19.7x10^3 km
Orbital period: 6.39 days
Radius: 600 km
Mass: 0.1 pluto masses
Pluto is theorized to be not an asteroid, but a chunk from the Kupier
(Sp?) disk. Both Pluto and Charon are composed of ice/rock very similar
to a comet, only much larger.
Mike
--
Michael Varney
Department of Physics
Colorado State University
*************************************************************************
If as*holes could fly, it would be perpetually dark!
Of course, one kind person will lift the darkness.
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mcva...@holly.colostate.edu
Of course, since there's no widely-accepted definition of a planet, one can
define the term in such a way to have the desired number of planets in the
solar system, from zero on up. In other words, it's a debate with very
little value.
--
Jeff Foust |
EAPS Dept., MIT | "God is really just a grad student from another
je...@astron.mit.edu | universe who created our universe for his thesis.
jfo...@mit.edu | Probably going to get a D, too." -- Larry Klaes
http://reudi.mit.edu/ |
SpaceViews newsletter: http://www.seds.org/spaceviews/
>It is not an asteroid. Many astronomers argue that being a sphere and
>having a moon makes it a planet. Many other astronomers, like me,
>don't want to call it a planet anymore and want some new word for it.
Are you an astronomer?
How many astronomers do you know of that want to have a new word for it?
Just curious.
__________________________________________________________________________
Rolf Meier usual disclaimer applies
Charles Vegman <veg...@aztec.asu.edu> wrote in article
<50od9v$4...@nnrp1.news.primenet.com>...
> My brother in law told me recently that Pluto is now considered by most
> astronomers to be an errant asteroid. True? Hmm...I recall discussions
> a few years back about Pluto being a small planet, perhaps having a
satelite
> of its own, and other minor details, but I don't recall this
revelation....
>
> Vegman
>
I highly doubt that "most astronomers" give a dip! There are a few very
vocal advocates of calling it other than a major planet. Most of the
astronomers that I have talked to say why bother causing all the confusion
over a name change, give Clyde his due and work on real problems.
And that attitude seems reasonable to me.
>Mass: 0.0018 Earth Masses
Where did you get tha? I calculate a mass of 0.002460 Earth Masses,
based on the orbit of Charon.
http://michele.gcccd.cc.ca.us/~ljohnson/johnson.html
>>It is not an asteroid. Many astronomers argue that being a sphere and
>>having a moon makes it a planet. Many other astronomers, like me,
>>don't want to call it a planet anymore and want some new word for it.
>Are you an astronomer?
Yes.
>How many astronomers do you know of that want to have a new word for it?
I haven't taken a poll, but I know I'm not the only one. I guess I
exagerated when I said, "many other astronomers."
http://michele.gcccd.cc.ca.us/~ljohnson/johnson.html
Probably true.
>There are a few very
>vocal advocates of calling it other than a major planet. Most of the
>astronomers that I have talked to say why bother causing all the confusion
>over a name change, give Clyde his due and work on real problems.
Calling Pluto something else does not diminish Clyde Tombaugh's
accomplishment. He discovered the first of a new class of object.
That is more important than finding another planet.
>And that attitude seems reasonable to me.
I agree. There is no reason to get into a long, heated debate.
However you pronounce it, it's still Pluto.
http://michele.gcccd.cc.ca.us/~ljohnson/johnson.html
How readily accepted is this? I've read in many modern texts that
Pluto is more likely a moon from one of the gas giants that was
catastrophically disrupted some time ago.
--
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| Jeff Wilson | In space, no one can |
| jdwi...@nortel.com | hear you scream!! |
| Richardson, TX - my opinions are...MINE. | |
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>My brother in law told me recently that Pluto is now considered by most
>astronomers to be an errant asteroid. True? Hmm...I recall discussions
>a few years back about Pluto being a small planet, perhaps having a satelite
>of its own, and other minor details, but I don't recall this revelation....
>Vegman
I'm not an astronomer, nor do I know what 'most' of them think about
Pluto, but as I recall, there are 2 criteria for being called a planet
... 1) in orbit around the sun ( vs being in orbit around another
planet ) and 2) enough mass to have assumed a spherical shape ( vs
the 'potato shaped' Gaspra ). I think Pluto meets both of these
criteria, even though it's moon ( Charon ) is close enough in size
that many call it a 'binary system'. So far, it's still classified as
a planet.
george c
The mass as quoted in the CRC 1983 - 1984 on page f-165 is ~ 0.002?
The text Introductory Astronomy and Astrophysics #rd Edition by Zeilik
Gregory and Smith Gave the value I quoted in the previous post.
I am wondering, did you use approximations of the mass of the sun and
the average distance of Pluto when using Keplers Harmonic Law?
Mike.
Let us say that Pluto was once a moon of one of the gas giants.
The force and energy needed to rip Pluto from such an orbit to an orbit
farther away from the sun is astounding. The pull of the orbited gas
giant would make it very difficult to achieve this type of orbit.
Pluto also has a companion, Charon, that orbits Pluto. I wonder at
the type of mechanics needed to assure the orbit of Charon around Pluto
as Pluto was ripped away from the gas giant.
Pluto and Charon are made of the same material as comets and objects
from the Kuiper disk.
I thinks it is a better model to have Pluto a body from the Kuiper Disk
than a rogue satellite from a gas giant.
Pluto is the smallest of the nine "planets". Yes, it does have a
satellite, Charon, which is so large, that Pluto-Charon might better be
considered a kind of binary planet than a planet and its satellite.
It is now known that, outside the orbit of Neptune, there is a belt of
small objects, vaguely similar to the asteroid belt, but consisting
of icy things, rather than rocky ones. Some of these objects are of the
order of a hundred kilometres in diameter, and quite a few of them have
been seen. Sometimes these objects are perturbed by the planets and fall
into the inner solar system, where they appear as *comets*. Pluto,
because of its small size and its orbital charcteristics, is now
considered by many astronomers to be the largest member of this belt,
which is called the Kuiper Belt. So, according to them, it is neither a
planet nor an asteroid, but a very large proto-comet!
However, this is a slippery slope. Should we use the same logic to argue
that Mars is the largest asteroid? By conventional definition, a planet
is anything orbiting the sun that has a diameter of 1000 kilometres or
more. By this definition, Pluto is a planet.
dow
Several of the largest asteroids, e.g. Ceres, satisfy both of these
criteria, yet are still called asteroids.
A third criterion is having a diameter of 1000 kilometres or more. This
neatly excludes Ceres and all the other conventionally-called asteroids,
but includes all the objects we know as planets - including Pluto.
The truth is, of course, that there are no clear physical divisions
between planets, asteroids and Kuiper-belt proto-comets. Which objects
are included in each category is purely a matter of convention. This is
a discussion about words, rather than about any significant astronomical
facts.
dow
Ceres is not spherical, and does not have near enough mass to assume a
spherical shape.
Regards,
Ahhh yes... but with Charon you get two for the price of one... that's a
50 percent discount... surely Congress can't pass that up?
BTW: Please let's not start up this "is it or isn't it a planet" routine
again. The last one was quite boring.
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_ /| DISCLAIMER: Disclaimant is a hireling who speaks for himself.
\'o.O' He is as bothered and bewildered as you, and he
=(___)= Ack! probably didn't mean or say what you might have
U Thppft!! thought he meant or said.
---------------------------------------------------------------------
planette?
planetling?
baby planet?
plasteroid?
subplanetviceplanetasssistantplanetdeputyplanet
> This is really just a semantics word game (how do you define "planet"
> precisely anyhow? And why should I buy your defination insted of mine?
> It doesn't change anything about the object anyhow.)
Of course not. In fact the discussions is even less than an argument about
semantics. Planets are not defined with any specific size limit or
relationship to other bodies; they are defined by example. As such, Pluto is a
planet, pure and simple.
Arguing that Pluto is not a planet is something like arguing that an apple is
not a fruit.
--
Erik Max Francis, &tSftDotIotE http://www.alcyone.com/max/ m...@alcyone.com
San Jose, California ICBM 37 20 07 N 121 53 38 W R^4: the 4th R is respect
"Out from his breast/his soul went to seek/the doom of the just." -- _Beowulf_
In article <wa2iseDx...@netcom.com>, Robert Casey
(wa2...@netcom.com) writes:
>This is really just a semantics word game (how do you define "planet"
>precisely anyhow? And why should I buy your defination insted of mine?
>It doesn't change anything about the object anyhow.) BESIDES, Congress
>might decide to not fund the Pluto Express spaceprobe mission, if they
>thought Pluto was "demoted" from planet to asteroid. To Congressmen,
>words are the entire ballgame. And that an asteroid, being a "minor
>planet" isn't worth the money, where if that same object is called
>a "major planet" let's do it. Why make it harder to convince Congress
>to give us enough $ for this mission!!
>
Save the International Ultraviolet Explorer !
Fruits have a much better definition than planets.
And remember, a tomato is a fruit. Except for tax purposes in New
York.
No. Pluto Express hasn't progressed yet to the point where it becomes a
line item in the budget. Given current budgetary pressures that may not
happen for a few years, either. :( See:
http://www.jpl.nasa.gov/pluto/PFFinfo.html
for more info.
>In "Mining the Oort" Fred Pohl refers to
>"plutons" as a generic name - I don't know if this is generally
>accepted.
Cute name, but no, not in general usage.
--
Jeff Foust |
EAPS Dept., MIT | "Asking female officers for their clothing could
je...@astron.mit.edu | lead to misunderstanding."
jfo...@mit.edu | -- Tuvok, "Star Trek: Voyager"
> DAVID WILLIAMS wrote:
>> Several of the largest asteroids, e.g. Ceres, satisfy both of these
>> criteria, yet are still called asteroids.
>>
>> A third criterion is having a diameter of 1000 kilometres or more. This
>> neatly excludes Ceres and all the other conventionally-called asteroids,
>> but includes all the objects we know as planets - including Pluto.
> Some sources have given the diameter of Ceres as slightly above 1000
> km, which according to your definition would make Ceres a "planet"...
Such sources are woefully out of date. There is a very reliable
occultation diameter determination for Ceres that puts it at 933 km.
The ellipticity is only a few km either way from that figure; doesn't
put it over 1000 km.
You gotta be careful here. Kepler's Third Law gives the *sum* of the masses
of Pluto and Charon -- if you plug in 19640 km for Charon's semimajor axis
and 6.387246 days for Charon's orbital period, the system GM turns out to be
985 km^3/sec^2, or 0.00247 times Earth's.
In order to break this figure into Pluto's mass and Charon's mass separately,
you have to observe the two bodies orbiting around their barycenter well enough
to get the ratio of (Pluto minus barycenter) / (Charon minus Pluto). Given
that the two bodies are never separated by more than 1", this is a rather
tricky observation to make. It's possible with Hubble, but there are all sorts
of distortions in the optics (both the main telescope and WF/PC) to contend
with. It's been tried from the ground too, where the big technical difficulty
is in separating the blended images.
In any case, the Charon/Pluto mass ratio seems to be converging on a value of
about 1/8, so Pluto has about 8/9 of the mass of the system, and thus Pluto
itself has about 0.0022 of the Earth's mass.
References include:
G.W. Null and W.M. Owen, Jr. 1996. AJ 111,1368
L.A. Young et al. 1994. Icarus 108, 186
D.J. Tholen and M.W.Buie 1996. Icarus, in press
-- Bill Owen, w...@wansor.jpl.nasa.gov
> >> Some sources have given the diameter of Ceres as slightly above 1000
> >> km, which according to your definition would make Ceres a "planet"...
> Yes I know these sources are out of date, nevertheless they've appeared.
> Which means that if one sets a limit of 1000 km between "planet" and
> "asteroid", then Ceres would have been a planet a few decades ago, and
> then switched to being an asteroid....
In 30 years of planetary astronomy, I've never heard of any such criterion
being seriously applied.
What you call things is arbitrary. After all, the old Indo-European word
"planet" just means something that roams or wanders.
But if you want to find a genuinely significant distinction, it might be
an object which chemically differentiated after formation, versus one
that did not. In that case Mercury through Neptune, but also Vesta and
the parent bodies of some other differentiated asteroids would be planets,
but Ceres and Pluto probably not.
Ben
>>> DAVID WILLIAMS wrote:
>>>> Several of the largest asteroids, e.g. Ceres, satisfy both of these
>>>> criteria, yet are still called asteroids.
>>>>
>>>> A third criterion is having a diameter of 1000 kilometres or more. This
>>>> neatly excludes Ceres and all the other conventionally-called asteroids,
>>>> but includes all the objects we know as planets - including Pluto.
>>> Some sources have given the diameter of Ceres as slightly above 1000
>>> km, which according to your definition would make Ceres a "planet"...
>> Such sources are woefully out of date. There is a very reliable
>> occultation diameter determination for Ceres that puts it at 933 km.
>> The ellipticity is only a few km either way from that figure; doesn't
>> put it over 1000 km.
> Thanks for posting something that's NOT a discussion with "Nancy".... :-)
I've posted several items that don't involve Nancy. I've posted items that
involve you. In fact, you got so upset, you made a big stink about putting
me in your kill file. Yet here you are.
If it's implausible to use a 1000-km-diameter criterion to distinguish
planets from other stuff, then it's certainly implausible to use a
criterion that depends on the internal structure of the body. Without
rather extensive study, how does one know whether an object has
chemically differentiated? Until the studies have been done, what does
one call it?
In the case of our own solar system, it is probably enough just to have
a list of (presumably nine) objects, and say "By convention, these are
the planets." But the science of planetary astronomy is now extending to
objects in orbit around other stars. Sooner or later, presumably, small
objects will be found out there which, like our solar-system asteroids,
etc., will be felt to be too small to be called planets. It would be
nice to have a set of simple criteria for distinguishing planets from
these smaller objects that could be applied soon after discovery,
without awaiting the results of studies that might take decades to
complete. Then, when some super-telescope detects a pinprick of light
orbiting a star, we could say fairly quickly, "This is a planet.", or,
conversely, "This is an asteroid."
I suppose only the apparent brightness of the object, relative to its
distance from its parent star, is a usable criterion. Which boils down,
pretty well, to its size....
dow
>>> Thanks for posting something that's NOT a discussion with "Nancy".... :-)
>> I've posted several items that don't involve Nancy.
> Yeah, a few -- but most of your posts were responses to "Nancy",
> weren't they?
If you really want to know, Paul, be my guest to count them.
> Did you count them?
I don't care to. I'm not interested in keeping a scorecard.
> Well, someone else counted them for you:
Yeah, an anonymous person named "Foofy", who admitted to being a fool,
and who did lousy research. I didn't see any count of the several items
I posted that didn't involve Nancy, so the count is useless.
> You're not #1 on this list,
Irrelevant, Paul. I wasn't trying to be any number on the list.
> but if this guy had counted your messages
> all the way back to Jan 96, you might very well have made it #1....
Or you might have, given that you also responded to Nancy. Seems you
don't care to discuss your own involvement, only mine. I'm not
surprised, but I still don't understand your motivation.
>> I've posted items that involve you. In fact, you got so upset,
>> you made a big stink about putting me in your kill file.
> How old are you?
Irrelevant, Paul.
> Here you act as if you were no older than a teenager.
What you think is irrelevant, Paul. The fact that all you want to
discuss right now is Nancy speaks volumes. Note who brought up Nancy:
you, not me.
> Did it upset you very much that not everybody wanted to
> see all your responses to Nancy?
It didn't upset me at all, Paul.
>> Yet here you are.
> Sure! From time to time I clean up my killfiles.
Why? To remove the desired effect?
> As I noticed my
> count of killed files went down dramatically, I decided to clean up
> my killfiles. Nancy is gone for the moment, which means your
> responses to her should be gone too.
They are. But you had to make sure that Nancy would be brought up again.
Do you have some obsession with Nancy?
> But if you continue with
> posts like this, I'll killfile you again very soon.
Go right ahead, Paul. At least it would prevent you from bringing
up such useless topics again.