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Glom
2003-May-01, 10:33 PM
We've had loads of raging debates about the status of Pluto as a planet or a KBO. The question is, how would you answer if asked the question, "How many planets are in the Solar system?"

nexus
2003-May-01, 11:13 PM
I say there are nine, Pluto may be a planet for sentimental reasons only, but thats still a viable reason. Isn't it pretty unlikely that we will find a KBO larger than Pluto out there? There isn't really a problem unless we find something that is bigger, than there might be reason enough for Pluto to loose it's title.

cyswxman
2003-May-02, 12:17 AM
Hmmm...8 if you don't count Pluto...9 if you do...and 10 if you count Planet X. A trick question!! :wink:

DJ
2003-May-02, 12:42 AM
i have to stick with tradition until something of significant size is added

DJ

tracer
2003-May-02, 01:05 AM
Pluto, a planet? Bah humbug. It's a latecomer as planets go, not even disovered until the 1930s, and it's dinky little iceball sitting out right where we'd expect a KBO to be. It's got an orbit so eccentric it crosses inside the orbit of Neptune for a few years. It's the only "planet" whose orbit is significantly inclined with respect to the ecliptic. Heck, Ceres and Vesta are more "planet like" than Pluto is, and you don't see the IAU running around trying to get them classified as planets, do ya?

Pluto ain't no planet. It's a close-orbiting, low-eccentricity, high-mass Kuiper Belt object. Um ... with a moon.

Total number of planets in the Solar system: 8.

Reacher
2003-May-02, 02:22 AM
Here here!
I must agree.

gethen
2003-May-02, 02:32 AM
Nine, for sentimental reasons. I learned it when I was little. :roll:

ToSeek
2003-May-02, 02:34 AM
Pluto, a planet? Bah humbug. It's a latecomer as planets go, not even disovered until the 1930s, and it's dinky little iceball sitting out right where we'd expect a KBO to be. It's got an orbit so eccentric it crosses inside the orbit of Neptune for a few years. It's the only "planet" whose orbit is significantly inclined with respect to the ecliptic. Heck, Ceres and Vesta are more "planet like" than Pluto is, and you don't see the IAU running around trying to get them classified as planets, do ya?

Pluto ain't no planet. It's a close-orbiting, low-eccentricity, high-mass Kuiper Belt object. Um ... with a moon.

Total number of planets in the Solar system: 8.

You tell 'em, Tracer. ;)

Grand Vizier
2003-May-02, 03:14 AM
That's 9, but I'd increasingly start to emphasise 'major planets'. I just don't think it matters so much, except as a sort of mnemonic. The modern idea of the Solar System is so varied and complex that the count of planets is just one rather contrived part of it.

Plus counting out through the nine planets may make it easier to teach stages in astronomical history.

Having said that - what happens if (more likely when) we find a body larger than Pluto in the Kuiper Belt? That represents a problem that has to be dealt with. At that point the choices are 8 or 10, and I don't actually know which I'd go for right now. Till then, 9...

beskeptical
2003-May-02, 03:24 AM
The poll isn't written correctly. Shouldn't it be asking how many planets are known....? Isn't there some evidence for a tenth body orbiting out there? And if there isn't, it is still possible there are more.

As far as Pluto being a moon, an ice ball, or a planet, does anyone really care? I mean it might matter to someone whose specialty is defining planetary body classifications. But it doesn't matter to me. It doesn't change the nature of Pluto or the Solar system.

Does the definition we assign to Pluto affect the study of Pluto? If that were so then it might matter.

kilopi
2003-May-02, 03:57 AM
Nine. Although the last poll (http://www.badastronomy.com/phpBB/viewtopic.php?topic=4016&forum=1&48) came out dead even by my count, 16 to 16.


Heck, Ceres and Vesta are more "planet like" than Pluto is, and you don't see the IAU running around trying to get them classified as planets, do ya?
Hold it. Define planet first (http://www.badastronomy.com/phpBB/viewtopic.php?p=34053&highlight=ceres#34053), then you can throw around the term "planet like". Pluto is a lot bigger than Ceres and Vesta and Quaooeooarroar

Moose
2003-May-02, 11:55 AM
Besides, point out objects orbitting Ceres and Vesta the way Charon orbits Pluto.

Anything big enough to have a moon is big enough to be a planet in my book.

kucharek
2003-May-02, 12:02 PM
Anything big enough to have a moon is big enough to be a planet in my book.

Take care of your words. I just say Ida/Dactyl (http://www.solarviews.com/eng/ida.htm)

Harald

informant
2003-May-02, 01:18 PM
9, until proven otherwise. :P

poorleno
2003-May-02, 01:28 PM
Despite your wishes, there are nine planets in the solar system.
These are divided into two groups: the inner planets (Mercury, Venus, Earth, Mars) and outer planets (Jupiter, Saturn, Uranus, Neptune). Pluto doesn’t belong to those; however it’s still classified as a planet.

informant
2003-May-02, 01:35 PM
I say there are nine, Pluto may be a planet for sentimental reasons only, but thats still a viable reason. Isn't it pretty unlikely that we will find a KBO larger than Pluto out there? There isn't really a problem unless we find something that is bigger, than there might be reason enough for Pluto to loose it's title.


Having said that - what happens if (more likely when) we find a body larger than Pluto in the Kuiper Belt? That represents a problem that has to be dealt with. At that point the choices are 8 or 10, and I don't actually know which I'd go for right now. Till then, 9...

In my opinion, that would still depend on whether we establish that Pluto belongs to the Kuiper Belt or not.


Heck, Ceres and Vesta are more "planet like" than Pluto is, and you don't see the IAU running around trying to get them classified as planets, do ya?

Ceres was initially classified as a planet, then declassified - because it was realised that it belonged to a larger group of bodies. OK, also because of its size - which, as kilopi noticed, is considarably smaller than Pluto's.


Isn't there some evidence for a tenth body orbiting out there?

Turns out that there isn’t after all (http://www.badastronomy.com/phpBB/viewtopic.php?t=4064).


As far as Pluto being a moon, an ice ball, or a planet, does anyone really care? I mean it might matter to someone whose specialty is defining planetary body classifications. But it doesn't matter to me. It doesn't change the nature of Pluto or the Solar system.

Does the definition we assign to Pluto affect the study of Pluto? If that were so then it might matter.

Since “planet” is a technical term of astronomy, calling something a planet supposedly gives us technical information about it.

tracer
2003-May-02, 03:51 PM
Despite your wishes, there are nine planets in the solar system.
Suuuuuure, just keep telling yourself that.

kilopi
2003-May-02, 04:01 PM
Despite your wishes, there are nine planets in the solar system.
Suuuuuure, just keep telling yourself that.
What makes Ceres more planet-like than Pluto?

ToSeek
2003-May-02, 04:22 PM
Does the definition we assign to Pluto affect the study of Pluto? If that were so then it might matter.

I betcha if Pluto weren't classified as a planet we wouldn't be sending a probe there.

Kaptain K
2003-May-02, 07:26 PM
Four! :o

The Solar System consists of:
One star - Sol
Four planets - Mercury, Venus, Earth and Mars.
Junk (set one) - Main belt asteroids.
Four sub-dwarfs - Jupiter, Saturn, Uranus and Neptune.
Junk (set two) - KBO's.
Junk (set three) Oort cloud.
Junk (set four) - Comets and outer system asteroids (renegade KBO's and Oort escapees.
8)

kilopi
2003-May-02, 07:33 PM
Four planets - Mercury, Venus, Earth and Mars.
Junk (set one) - Main belt asteroids.
Four sub-dwarfs - Jupiter, Saturn, Uranus and Neptune.
You've got this backwards. We've found planets around other stars, and they're all like Jupiter. So, there are four planets, but their names are Jupiter, Saturn, Uranus and Neptune. Planets are sub-dwarfs.

I don't know what you'd call those tiny little piles of rock next to the Sun. Hey, maybe rockpiles. One of them sorta wet.

beskeptical
2003-May-05, 01:58 AM
As far as Pluto being a moon, an ice ball, or a planet, does anyone really care?

I forgot where I was posting. :roll: :lol:

aurorae
2003-May-06, 04:43 PM
What makes Ceres more planet-like than Pluto?

What makes Ceres less planet like than Pluto?

:-?

aurorae
2003-May-06, 04:44 PM
I betcha if Pluto weren't classified as a planet we wouldn't be sending a probe there.

NEAR?

http://near.jhuapl.edu/

kilopi
2003-May-06, 05:47 PM
What makes Ceres more planet-like than Pluto?

What makes Ceres less planet like than Pluto?
Tracer had said (http://www.badastronomy.com/phpBB/viewtopic.php?p=79993#79993), "Heck, Ceres and Vesta are more "planet like" than Pluto is," but Pluto (http://www.planetscapes.com/solar/eng/pluto.htm) has 15 times the volume that Ceres (http://www.planetscapes.com/solar/eng/asteroid.htm) has, and 81 times the volume that Vesta (http://www.planetscapes.com/solar/eng/asteroid.htm) has, so that is an obvious answer to your question. What is the reasoning going the other way?

PS: space.com article (http://www.space.com/scienceastronomy/planet_denitions_030227.html) about Basri's plan which would classify both Pluto and Ceres, but not Vesta, as planets.

BCstargazerr
2003-May-07, 04:03 PM
clyde tombaugh was hired to find planet x by blinking photographic plates. when he came across pluto, he had no idea of its size or mass. from his point of view ( pre-kuiper belt or oort cloud )he had found his planet x.
now that we know a little more about pluto and charon, we shouldn't demeans tombaugh's achievement

ToSeek
2003-May-07, 04:39 PM
I betcha if Pluto weren't classified as a planet we wouldn't be sending a probe there.

NEAR?

http://near.jhuapl.edu/

Asteroids are a lot closer and easier to get to. If Pluto were treated as just another KBO, it would probably be a lot lower on the priority list. A lot of the public support for the Pluto mission comes from the fact that it's the only planet that hasn't been visited yet.