The Ur-Quan Masters Discussion Forum

The Ur-Quan Masters Re-Release => Starbase Café => Topic started by: Megagun on August 24, 2006, 06:31:51 pm



Title: Pluto is no longer a planet! Poor Fwiffo!
Post by: Megagun on August 24, 2006, 06:31:51 pm
http://en.wikipedia.org/wiki/2006_redefinition_of_planet

Discuss!


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Defender on August 24, 2006, 07:01:11 pm
This is pure crap. Galileo must be rolling over in his grave. Why the hell do we have to classify everything? We have 9 planets, 10 if an object is truly past Pluto. There is no discussion for me IMO.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: XR4-IT on August 24, 2006, 07:45:00 pm
I am just coping my blog article to here so I don’t have to retype every thing.

The Eight Planets
Over the past week the debate has continued and the astrologers I mean astronomers have determined a new definition of a planet.    “(1) A planet1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.”   
With that Pluto has been stricken from the planet list because it dose not “clear the neighborhood around its orbit” this is because the orbit of Pluto crosses that of Neptune’s.  If that is the case why then is Neptune still a planet? It overlaps Pluto’s orbit.

Pluto is still however being called a dwarf planet under the new definition of a dwarf planet.

“(2) A dwarf planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.”

Apparently these dwarf planets are still not planets; making the list of Sol’s planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and possibly Neptune.

It seems to me that the new decision on what is a planet was made more for history and culture then for science, because you could still find a celestial body that is in orbit around the Sun with mass sufficient to overcome rigid body forces so that it assumes a … nearly round shape and has cleared the neighbourhood around its orbit that is still smaller than Pluto, and must by definition be called a full blown planet.  So how is it that we call Pluto a dwarf planet, and this smaller thing a full planet.

I thought that this was an interesting quote form the article I read on the subject.

He had argued that Pluto and similar bodies didn’t deserve planet status, saying that would “take the magic out of the solar system.”

This really just means that it was too hard for the astrologers to figure out our horoscopes with 12 planets to worry about.

 

Edit ---

After rereading the new definition it struck me that it said a celestial body that is in orbit around the Sun (Sol I’m assuming) instead of a star. This could mean that a object orbiting another star could not then be a planet.

Later-

 

XR4-IT



Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Death 999 on August 24, 2006, 08:12:09 pm
With that Pluto has been stricken from the planet list because it dose not “clear the neighborhood around its orbit” this is because the orbit of Pluto crosses that of Neptune’s.  If that is the case why then is Neptune still a planet? It overlaps Pluto’s orbit.

Nice try, but Neptune has coerced Pluto's orbit to be a subharmonic of its own (1.5 times its own), so it is 'cleaned up' nearly as much as if it were in a lagrange point.


After rereading the new definition it struck me that it said a celestial body that is in orbit around the Sun (Sol I’m assuming) instead of a star. This could mean that a object orbiting another star could not then be a planet.

I think this is a mere oversight, of course planets can orbit other stars.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: XR4-IT on August 24, 2006, 09:04:17 pm
After rereading the new definition it struck me that it said a celestial body that is in orbit around the Sun (Sol I’m assuming) instead of a star. This could mean that a object orbiting another star could not then be a planet.

I think this is a mere oversight, of course planets can orbit other stars.

Yes… I just thought that it was funny because they did make it clear in last weeks definition that it was to be orbiting a star.

Also I saw this video on msn.

http://video.msn.com/v/us/msnbc.htm?g=D77DEA89-2B81-48EF-95DD-9F35A37B610F&f=00&fg=copy

I though that it is was funny because it says that the Milky Way now has 8 planets.   


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: GeomanNL on August 24, 2006, 10:48:55 pm
R.I.P.
 :'(


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Zeep-Eeep on August 24, 2006, 11:22:49 pm
Seems kind of silly. I mean, am I going to point to a chart with nine planets on it
and say to the grand kids, "I remember when we had nine planets and
they were good enough fo us"?
We've got nine of the things, leave 'em be.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Deus Siddis on August 25, 2006, 02:46:19 am
"Ca-chink"

(The sound of my respect for modern science dropping down another notch.)


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Arne on August 25, 2006, 01:16:04 pm
I don't like the 'clears its orbit' citeria at all, but I agree with 8 planets.

How about... "massive enough to potientally have a significant atmosphere" for planets, and "massive enuogh to be round" for planetoids/dwarf planets? Sorta fuzzy, but no more than 'cleaing orbits'.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Shiver on August 25, 2006, 02:13:53 pm
Just a bunch of technicalities. I think the dwarf planet thing makes sense seeing as how we've been spotting so many asteroids and ex-moons that could qualify as planets recently.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: XR4-IT on August 25, 2006, 04:09:41 pm
I don't like the 'clears its orbit' citeria at all, but I agree with 8 planets.

How about... "massive enough to potientally have a significant atmosphere" for planets, and "massive enuogh to be round" for planetoids/dwarf planets? Sorta fuzzy, but no more than 'cleaing orbits'.

You realize that cutting out planets that don’t have an atmosphere would cut out Mercury.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Death 999 on August 25, 2006, 04:11:47 pm
That is the only reason this happened. If Pluto didn't have a lot of friends around, it'd be fine. But at the rate they're finding them, we'd expect to find around 100 pluto-scale objects out in the kuiper belt.

In other words, it wouldn't by MVEMJSUNP, it would be MVEMJSUNPABCDEFGHIJKLMNOP QRSTUVWXYZABCDEFGHIJKLMNOP QRSTUVWXYZ ABCDEFGHIJKLMNOP QRSTUVWXYZ ABCDEFGHIJKLMNOP QRSTUVWXYZ.
(space breaks inserted to preserve sanity)

Got it?


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: XR4-IT on August 25, 2006, 05:16:28 pm
That is the only reason this happened. If Pluto didn't have a lot of friends around, it'd be fine. But at the rate they're finding them, we'd expect to find around 100 pluto-scale objects out in the kuiper belt.

In other words, it wouldn't by MVEMJSUNP, it would be MVEMJSUNPABCDEFGHIJKLMNOP QRSTUVWXYZABCDEFGHIJKLMNOP QRSTUVWXYZ ABCDEFGHIJKLMNOP QRSTUVWXYZ ABCDEFGHIJKLMNOP QRSTUVWXYZ.
(space breaks inserted to preserve sanity)

Got it?

I would have rather had that then the definition we got… I don’t think this is the end of the planet debate as there is nothing stopping other scientific communities from making there own definition of what a planet is.

If we are going to have dwarf planets they should have given a size qualifier.  As it is you could still have my full planet that is smaller than Pluto so there are still holes in there plan.   


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Cronos on August 25, 2006, 05:23:56 pm
**puts foot down**

Pluto is a planet, now and forever...

At least to me  :-[


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Draxas on August 25, 2006, 06:15:42 pm
I think they're just prejudiced against little peo... er, planets.

We'll miss you, Pluto.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Anthony on August 25, 2006, 06:45:03 pm
I was about to make a post about this....  :)

Anyways, it's not really that fatal that Pluto is no longer a planet.  It's just that now every video game, book, television show, and movie set in the future are now incorrect.

Which makes me wonder... Will they include this little fact in the new Star Control game?

And those three new planets that have been discovered, maybe that will make some interesting new adventures if this was also added to the new Star Control.

But about Pluto, it's just another interesting fact to think of when you're thinking about space...

And yea, poor Fwiffo.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Arne on August 25, 2006, 07:34:20 pm
XR-something> No. I didn't necessarily cut out Mercury, I said 'potentially'. To clarify:

It's a planet if:

A.) The body has a significant atmosphere.
or
B.) The body is massive enough to potentially have a significant atmosphere, but does not have one.

(and it's not a black hole, sun, artificial object or moon, etc.)

(Note that the 'or' will allow for bodies not massive enough to have an atmosphere but still has one because of some freaky setup.)


I have no idea where to put the threshold for atmosphere. Maybe a bit under Mars. Mercury might not qualify as a planet with my definition. When I think of planets I think rather large things that Star Trek away teams land on, not rocks. Mercury is a rock. Mercury is boring.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: XR4-IT on August 25, 2006, 08:07:21 pm

(Note that the 'or' will allow for bodies not massive enough to have an atmosphere but still has one because of some freaky setup.)

Well in that case 2003 UB313 (Xena) is thought to have an atmosphere.

“We think that the bright surface and uniform white coloring of the planet both have the same cause. Right now the planet is as far away from the sun as it ever gets, and thus as cold as it ever gets. At this distance from the sun even the planet's atmosphere is frozen solid. (In fact if the earth were brought that far away from the sun its atmosphere would freeze solid, too!). In 280 years the planet will be the closest it ever gets -- a factor of almost 2.6 times closer. The absolute temperature on the planet will rise over the next 280 years by a factor of  1.6 (which is the square root of 2.6). The current temperature of (a quite cold) 405 degrees below zero will be but a distant memory at this point when the temperatures will be a balmy 360 degrees below zero. While both of these temperatures seem frigid beyond imagination, to methane and nitrogen (the likely components of the atmosphere of the planet), the difference between the two is the difference between frozen solid and evaporating into the atmosphere.”

This was taken from this site http://www.gps.caltech.edu/~mbrown/planetlila/


I have no idea where to put the threshold for atmosphere. Maybe a bit under Mars. Mercury might not qualify as a planet with my definition. When I think of planets I think rather large things that Star Trek away teams land on, not rocks. Mercury is a rock. Mercury is boring.

Mercury may be boring but its still a good place to get radioactives


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Deus Siddis on August 26, 2006, 03:53:37 pm
Quote
That is the only reason this happened. If Pluto didn't have a lot of friends around, it'd be fine. But at the rate they're finding them, we'd expect to find around 100 pluto-scale objects out in the kuiper belt. . .Got it?

Yes, I do. Scientists are afraid they would have to think of more names for planets so they changed the definition of "planet" to an illogical one so that pluto, its neighbors, and everything else discovered henceforth would be excluded from it.


Quote
Anyways, it's not really that fatal that Pluto is no longer a planet.  It's just that now every video game, book, television show, and movie set in the future are now incorrect.

Except for Starflight, which had only the first 8 planets orbiting Sol.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Terrell on August 27, 2006, 02:50:04 am
Fwiffo still has something to park his ship on, Pluto just isn't called a planet anymore.  Perhaps it should be called a Kuiper Belt Object, since that makes the most sense based on what we currently know, same for 2003 UB 313 (Xena).  Had Pluto been discovered today, based on current knowledge we wouldn't have classified it as a planet.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Death 999 on August 27, 2006, 07:01:26 pm
Not only that, but Fwiffo's hiding place is better since it is less popularly known-of!


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: grayfox777 on August 28, 2006, 07:31:19 am
Pluto is a planet. It's a dwarf planet. It's just not a main planet like the jovian and terrestial planets. It's not one of THE planets anymore.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Terrell on August 30, 2006, 06:16:40 am
One thing's for sure, I'm glad that the New Horizons spacecraft has been launched before the demotion, but I do think that the demotion was the correct decision.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Death 999 on August 31, 2006, 04:05:14 pm
What, you don't seriously think New Horizons would have been cancelled just because they demoted Pluto, surely? It would be the first mission to a Kuiper Belt Object, which is even more presigious!


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: XR4-IT on August 31, 2006, 06:13:00 pm
What, you don't seriously think New Horizons would have been cancelled just because they demoted Pluto, surely? It would be the first mission to a Kuiper Belt Object, which is even more presigious!

When will that get to pluto?


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Death 999 on September 01, 2006, 04:54:34 pm
Beats me... google... launched January 19, 2005...  arrival July 2015.

It'll fly by Jupiter to get a gravity assist next year.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: RTyp06 on September 06, 2006, 02:40:05 am
Do you guys realize we are finding many new planets in the kupier belt? Quoar, Xena(2003 UB 313 ) and her moon Gabrielle,Sedna, Quoar etc. etc. They expect to possibly even find mars size planets out there. The planet definitionary waters will be muddied further in years ahead.

http://www.nasa.gov/vision/universe/solarsystem/planet_like_body.html

I may be the minority, but I don't have a problem with the International Astronomical Union 's planetary definitions.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Lukipela on September 06, 2006, 07:23:00 am
Another Mars sized planet woudl indeed be interesting. Pity they are so far out from the sun though.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Mugz the Sane on September 06, 2006, 08:23:57 am
It means cities will be entirely self-contained and a significant portion of the colony power/resource output will be dedicated to life-support. It could be done, although the only purpose would be scientific research. Unless an industrial colony is dropped onto a VERY rich mineral deposit... it would be far more practical to strip-mine the asteroids. Easier too.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: RTyp06 on September 07, 2006, 12:04:29 am
Well we should know much more about Pluto, Charon and other kupier belt objects if the New Horizons, Pluto-Kuiper Belt mission is successful. Hopefully that will finally settle the case.

http://www.nasa.gov/mission_pages/newhorizons/main/

I'm looking forward to 2015!


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: SanderScamper on September 11, 2006, 01:41:18 pm
You're all overreacting, this is just the natural progression of how real science goes on. Imagine if we didn't make this desision now and when the time came to go to other solar systems it would be a significant problem, you should be happy it's resolved now and hopefully forever. Just because you grew up with the idea of Pluto being a planet don't make it so. What they've done is remove all the niggling little perspective problems, which is what science should be doing. The physical laws of the universe ovveride our opinions and science is reflecting that by dictating the definitions of planetary status upon those laws.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Draxas on September 11, 2006, 05:03:43 pm
But the definition remains, as it always has been, completely arbitrary.

And anyone who thinks that New Horizons would have made it to the launch phase if Pluto had been declared a "dwarf planet" 10 years ago is crazy. It would have been deemed unimportant to the non-scientists who decide the budgets for these projects, and would have been passed over for something "more significant." Just because it's small and hasn't cleared its orbit, doesn't mean it's any less interesting than the other planets.

I don't know, regardless of definitions, I'll miss seeing Pluto in our solar system from here on out. Because, simply put, it's only a matter of time before it's eliminated from the popular conciousness. After all, how many obscure, unpronouncable names can the average schoolkid memorize from the Kuiper Belt?


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Deus Siddis on September 11, 2006, 09:40:03 pm
From SanderScamper
Quote
You're all overreacting, this is just the natural progression of how real science goes on.

The development of new technologies is a much better example of "real" science than the simple wasting of funding it takes to fly doofs from around the world to a conference where they decide what to reclassify large spheres of matter, based on a show of hands.


Quote
Imagine if we didn't make this desision now and when the time came to go to other solar systems it would be a significant problem, you should be happy it's resolved now and hopefully forever.

Yea, we can't travel to other systems because we wouldn't know what to call the planetoids there. Oh no wait, that's not the reason, its because the scientific community is working hard on its rock ball definitions instead of developing the tech that might someday get us there. :P


Quote
The physical laws of the universe ovveride our opinions and science is reflecting that by dictating the definitions of planetary status upon those laws.

No, I don't think those laws, or there understanding of them has changed. This change seems to be a matter of opinion, not mathematics.


From Draxas
Quote
It would have been deemed unimportant to the non-scientists who decide the budgets for these projects, and would have been passed over for something "more significant."

I'm not sure if most non-scientists feel there is much significance to this mission be it to a planet or not. We really only care about life beyond this world, anything else is quite dull at this point (iow, no interstellar missions, no colonization/terraforming) to your average non-scientist.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Draxas on September 12, 2006, 04:49:21 pm
Quote
Quote
It would have been deemed unimportant to the non-scientists who decide the budgets for these projects, and would have been passed over for something "more significant."

I'm not sure if most non-scientists feel there is much significance to this mission be it to a planet or not. We really only care about life beyond this world, anything else is quite dull at this point (iow, no interstellar missions, no colonization/terraforming) to your average non-scientist.

Perhaps, but we lack the capabilities to travel beyond our solar system, and there's a good possibility we're not going to find life on any planets within it besides Earth. So, until we develop some kind of technology that allows us to travel at relativistic-scale speeds, we're stuck with learning as much as possible about the worlds we can reach in our lifetimes. Unless you're saying that space is not worth exploring until we find life on other planets? Or that we should only stick to examining worlds that would harbor life "as we know it"? In either case, that seems a vote against our entire space program.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Deus Siddis on September 12, 2006, 06:14:04 pm
Quote
Unless you're saying that space is not worth exploring until we find life on other planets?

No, that doesn't make any sense, unless you put faith in "SETI," a joke though it may be.


Quote
Or that we should only stick to examining worlds that would harbor life "as we know it"?

That would be a good place to start. After that, you can shoot for alternative forms of life. But NASA is probably afraid that if they did put out a good effort and discovered that there really is no life in this system beyond earth, for sure, their funding would drop off the cliff that is the average person's limited interest in rock/snowball exploration.

That is, unless you had mining, terraforming, or interstellar exploration, all of which are still a long ways off (even mining.)


Quote
In either case, that seems a vote against our entire space program.

If by that you mean "entire extra-earth-orbit space program," then yes. Which would help explain the lesser funding and interest payed to organizations like NASA, of late.


Now don't get me wrong, I do enjoy reading more about planets and nanotech in science news than about how an animal I know is intelligent, is intelligent, or about all the new diseases modern technology has caused and their corresponding experimental pharmaceuticals. But I think most people do not find this sort of exploration for the purpose of exploration to be very worthwhile or interesting.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Mugz the Sane on September 13, 2006, 08:49:11 am
Absolutely. Arbitrary indeed.

Now, instead of us parking off here on a large ball of wet rock arguing about what is or is not a planet, why don't we go take a look? If I like the weather there, I might just settle.

I mean, really, it IS the 21st century already!


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Shiver on September 14, 2006, 08:23:06 am
AND IT'S OFFICIAL! UB-34642615135 or whatever it was called has been renamed "Eris". Serves everyone right for thinking a C-grade daytime TV show that got canned years ago deserves a planet named after it.


Title: pluto
Post by: danica180 on October 09, 2006, 11:36:57 am
Pluto has been demoted by scientist into a minor planet which only means that there are only eight  major planets in the solar system.  It is unlikely that Pluto's status in the future will be return to planetary.


Title: Re: pluto
Post by: Lukipela on October 09, 2006, 12:18:04 pm
Pluto has been demoted by scientist into a minor planet which only means that there are only eight  major planets in the solar system.

Really? That sure is news to me. Are you absolutely sure?


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Draxas on October 09, 2006, 05:29:58 pm
Incase anyone didn't notice (check the sig), that was a spambot.

Is it just me, or are these things getting more obnoxious by the day?


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Rogue Kohr-Ah on October 09, 2006, 05:49:19 pm
The definition for planet is about as arbitrary as any other definition, and it hanges constantly to reflect political and cultural influences and pressures of the time.  Anyone who thinks the redefinition was a scientific effort is deluding themselves.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: meep-eep on October 09, 2006, 06:08:21 pm
Incase anyone didn't notice (check the sig), that was a spambot.
Hmm... I missed that. Deleted the spam and the user, but kept the rest of the note so that what follows still makes sense.

Quote
Is it just me, or are these things getting more obnoxious by the day?
It's not just you.

Although I've seen plenty of other users resurrecting threads only to say something that has been said before. Perhaps I should check those old notes for invisible links...



Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: definite on January 11, 2007, 01:42:17 pm
Guys, think about this:

If we do find 2 or more jupiter-sized heaven bodies sharing the same orbit (failed to clear paths of each other), will we call them dwarf planets?


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Death 999 on January 12, 2007, 05:00:30 pm
That situation is not dynamically stable. They would pull on each other and eventually collide or gravitationally scatter until they weren't in the same orbit as each other.

You could do that with a Jupiter-sized planet and an Earth-sized planet, though, perhaps (there is a minimum mass ratio). What would we call that Earth, then? A trojan companion of the Jupiter. Perhaps we'd invent the term 'companion planet', which is lower in status, like 'dwarf planet', than a regular planet.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Mugz the Sane on January 13, 2007, 10:21:06 am
Or we'd call it a moon.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: definite on January 13, 2007, 11:50:21 am
That situation is not dynamically stable. They would pull on each other and eventually collide or gravitationally scatter until they weren't in the same orbit as each other.

You could do that with a Jupiter-sized planet and an Earth-sized planet, though, perhaps (there is a minimum mass ratio). What would we call that Earth, then? A trojan companion of the Jupiter. Perhaps we'd invent the term 'companion planet', which is lower in status, like 'dwarf planet', than a regular planet.

There is at least one exception, though. If those two ``planets'' are located at the opposite side of sun (they are collinear, and sun is in the middle ), have identical masses, and the shared orbit is a perfect circle.

IMHO, the ``dwarf'' implies small in size.  Otherwise when we meet Umgah, they will probably say, ``You call that big thing dwarf  planet? Good joke, better than the Maus tank!''


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: RTyp06 on January 16, 2007, 01:26:03 am
I'm not sure if pluto is going to be demoted or Ceres promoted...Too much controversy over the astronomical union's "decision" . So...

I think anything with enough gravity to form a globe and orbits the sun should be called a planet. Yes that means the asteroid Ceres that orbits between mars and jupiter.

If our solar system has thousands of these in the kuiper belt, then YES, we have thousands of planets. For clarity it could be broken down into inner (Mercury  thru Mars), middle (Jupiter thru Neptune) and Outer (Pluto, Charon and beyond)

Systems like Pluto-Charon where one planet does not clearly orbit the other and both orbit around a point in space should either be called co-planets or whichever is larger called the planet and the smaller called the moon.

This makes the most sense to me.


Title: Re: Pluto is no longer a planet! Poor Fwiffo!
Post by: Death 999 on January 23, 2007, 05:19:55 pm
That situation is not dynamically stable. They would pull on each other and eventually collide or gravitationally scatter until they weren't in the same orbit as each other.

You could do that with a Jupiter-sized planet and an Earth-sized planet, though, perhaps (there is a minimum mass ratio). What would we call that Earth, then? A trojan companion of the Jupiter. Perhaps we'd invent the term 'companion planet', which is lower in status, like 'dwarf planet', than a regular planet.

There is at least one exception, though. If those two ``planets'' are located at the opposite side of sun (they are collinear, and sun is in the middle ), have identical masses, and the shared orbit is a perfect circle.

Though that is a stationary point of the system, it is unstable. If one of the planets were to be deflected a single angstrom inward, it would be more strongly attracted by the other planet, fall into a faster, closer orbit... by one angstrom... and then two... and four... within a few thousand years the other planet would no longer be in place. There are three such unstable points (one as you described, with equal masses; and for much lighter masses, one between us and the sun, and one further out).

There are also two stable points, sixty degrees around our orbit (one ahead, one behind). If you deflect it from those points, it sort of wanders around in circles but its deflection does not get worse.
These are what I was referring to.