How many planets are there in the solar system?
 

No, it's not the latest question from jbmagic ...

http://news.yahoo.com/s/ap/20060816/...me/new_planets

The International Astronomical Union is meeting this week and allegedly will finally address the status of Pluto and other celestial bodies.

The hubbub before the conference was that Pluto and its moon Charon (which is less of a moon and more of a binary asteroid system given their size and that the two rotate in unison so that the same face of each body is always facing the other) would be reclassified into a new category along with some of the other larger asteroids and celestial objects in the asteroid belt and Kuiper belt.

Now comes this proposal that the media is jumping on that would not only maintain Pluto as a planet but promote Charon, Ceres and Xena to planets as well. Ceres is believed to be the largest object in the asteroid belt, and Xena is a planetoid object in the Kuiper belt beyond Pluto. Ceres was originally classified a planet in the 1800s when it was discovered, then quickly demoted when astronomers came to their senses and realized that it was much smaller and erratic than the other planets.

I could live with Pluto remaining a planet status to maintain the status quo, but to simply say that because we call Pluto a planet that everything the same size or larger than Pluto is a planet just compounds a bad mistake.

I really hope this proposal gets changed.

Cue jokes about the 7th planet...

What did Neptune say to Saturn?

Give me a ring sometime!


Oh you cued up the 7th planet jokes....

I don't claim much knowledge abou such matters, but I got the sense that the IAU group mostly went in with an approach to define planet in such a way to include Pluto, at basically any cost.

What I heard this morning on NPR was that their proposed definition hinged on shape -- that an opbect with sufficient internal gravity to develop a round shape shoudl be classified as a planet, and anything oddly shaped would not be. Passes my common sense test, I guess, but I can't help but feel like there might be a more sensible definition that might involve distance or orbit duration or somesuch that might have been rejected on the sole grounds that it left Pluto out.

If a mass in space is possible to land on, has significant properties, and rotates around the sun... that's what a planet is to me. I don't know much about such things, like QuikSand said above, but how can an asteroid belt have planets in it? Am I being narrow-minded?

How do you know that Saturn was married more than once?

She has lots of rings.

What do the starship Enterprise and toilet paper have in common?



Both go past Uranus and pick off Klingons.

The title of this thread if jbmagic started it:

"How many Planets in solar System?"

What better more or less Planets?

If planet Pluto? Or not?

Why everyone hate planet?

That definiation would exclude the 4 biggest planets in our solar system, btw.

I was thinking somewhere along the lines of mass and the shape of the orbit. All planets have an elliptical orbit, but for laymen's purposes, you could say they are circular (they aren't so elliptical that you wouldn't be far from correct if you drew their orbit as a perfect circle) . But that would leave out Pluto which has a far more elliptical orbit than the other planets.

Not only that, but, again no planet orbits one the same "plane" as another planet, but again, you wouldn't be far from correct if you put them all on the same plane. Pluto's "plane" is very different from the rest.

I agree with you that they were trying the best they could to include Pluto as a planet, but try to exclude the other KBOs from the definition.

dola,

Here's Phil Plait's take on it: http://www.badastronomy.com/bablog/

This comment from his blog sums up my feelings on this whole debate: This is all incredibly silly.

Sorry, I didn't mean that we have the technology to do it. I just meant that in terms of size. If there's something out there the size of a golf ball that isn't being pulled into whatever it's circling around, that's still not a planet to me. :)

Yeah, I know what you mean. It's not every day I get to show off my geeky astronomy knowledge. :D

And it's not a question of technology, gas giants do not have a surface that you can "land on" at all. They have a liquid core, because of the immense pressure inside, but as you go down, it very, VERY gradually goes from gas to liquid. IOW, there's no point where it suddenly goes from atmosphere to land or ocean like on our planet or other rocky masses.



Hello, my name is sabotai and I am an astronomy geek.

If that is the rationale and objective of the IAU, I am very disappointed.

The problem is that if lower the standard of what is a planet to include Pluto and you let in Ceres, Xena and Charon based on spherical shape and size, then we're going to end up with an ass load of planets one day because we're likely going to find larger Kuiper belt objects. We may even find the occassional comet or asteroid that fits that definition.

One report has characterized the IAU definition as essentially any spherical object that orbits the sun. The Pluto/Charon binary "planet" orbits the sun in a similar fashion that the moon and the Earth orbit the sun. The moon is larger than either Pluto or Charon. Does that make the moon a planet?

As I said before, I'm not opposed to a definition that makes an exception for Pluto -- although because "public sentiment" wanting Pluto to remain a planet is not a good enough reason for me. But it seems that if you're going to define what planet is, size, shape and orbiting the sun is simply not enough. Orbital plane and circumference should be factors as well. To be honest, however, I'm not sure I can develop a definition of a planet that would exclude Ceres as a planet unless you establish a minimum size requirement -- or you specificy that an object must be shperical, not "almost" spherical -- then you can throw Ceres, Pluto/Charon and Zena in the trash.

Do you have a group meeting or a newsletter? :)

I'm in the math club, uh, the latin, and the physics club... physics club.

Well, in physics we... we talk about physics, properties of physics.

Ah, crap. Everything he says largely goes double for me. I hate this whole Planet, Dwarf Planet, "Pluton" nonsense.

I do think we can have a classical definition of what a contemporary planet is without going nuts. I quibble with him on being able to come up with a exception for every rule you could come up with. I think we can limit the definition in a way without creating chaos; but I think establishing multiple classes of planets is much more chaotic.

Did your cousin Kendall ever start eating really weird foods?

I'm sorry, you lost me at physics. However, I will admit to being a mathlete until junior high when the math got too boring. I was a Literature Bowl and -- dear god -- Economics Bowl -- participant, however. I'm glad our Economics Bowl team wasn't very good.

All this astronomy talk has me thinking, which I don't do often, especially about stuff like astronomy. So I am eager to ask some really basic astronomy questions that will leave all the hardcore people here giggling at my foolishness (and probably most non-astronomy buffs as well).

If a planet orbits the sun, and moons orbit planets, can anything orbit moons? And if a moon has moons, is it a planet? And can we say with certainty that the galaxy itself is not orbiting something else?

didn't they cover all this on Star Trek at some point?

Yes, no, no.

and no.

Guys who know nothing about astronomy also tend to know nothing about Star Trek.

*giggles at Fidatelo's foolishness*

Theoretically, of course. But I would think, generally, the gravity of the planet would orverride the gravity of the moon and either pull to object away from the moon and cause it to orbit around/crash into the planet, or cause it to be ejected away from both of them.

After thinking about it for a minute, I could see it. But as with the relationship of moon to planet to sun, the moon would have to be pretty far away from the planet, and the moon's moon would have to be pretty close to the moon for it to retain the body. Given the distance required, it might be possible for some of the moons of Jupiter or Saturn that are really far away from their planet to pick up some very small, minor body. But it would have to be exactly the right set of circumstances for it to happen.


No. Even though there is this large debate over what a planet is, that it has to be orbiting the sun is a pretty consistant parameter.


OUR galaxy? No, it's not orbiting anything. We'd be able to observe that pretty easily, given what the size of something would have to be in order to have our galaxy orbiting it.

But, our galaxy does have several much smaller galaxies orbiting it. I think, anyway. I know there are several minor galaxies close to ours. I'll have to double check on if they are actually orbiting our galaxy or not. EDIT: Yes, our galaxy does have several "dwarf galaxies" orbiting it.

Thanks Sabotai, that was very informative!

According to IAU's definition, if point around which the two bodies orbits is inside one of the bodies, the other is not a planet. Thus, the moon fails that test. They are considering Pluto and Charon a double planet because they orbit around a point outside either of them.

gold

Godspeed!

So it's sort of social. Demented and sad, but social.

Too bad, I was looking forward to the new age of 13 planets.

I hope they get to replacing the solar system placemats that are in circulation. I don't want my kids staring at dated information!

Pluto is getting screwed!

Sorry, I didn't have a picture of that, so I went with the one above.

The Hubble telescope captured an interesting image of Pluto just moments before it was removed from planetary status:

I never realized that Pluto was smaller than our moon. What a punk ass "planet." I've seen women's butts bigger than our moon.

Her butt was like Pluto...small and firm.



I have the poetry spilling out of me.

I guess the answer to this question is 8.

http://news.yahoo.com/s/space/200608...olongeraplanet

This is going to seriously hamper Pluto's bid for the 2016 Olympics.

A spontaneous anti-Earthling riot has just broken out on Pluto!!! Ice cubes are being thrown at ice carvings made to look like Earth!

OK, your challenge is to come up with a replacement mnemonic device for remembering the planets, to replace:

My Very Educated Mother Just Showed Us Nine Planets

...leaving off the last P, of course.

Go!

Easy, just abridge the most common variant, I think...

Mary's
Violet
Eyes
Make
John
Stay
Up
Nights

They have a stronger shot at landing the Miss Universe contest, I'd think.

Never heard that one. ANd I was hoping for something a little more comical.

Or...

Mary's
Vagina
Easily
Makes
John
Stay
Up
Nights

This should be submitted as a case for Pluto. A song from one of my favorite now-broken up bands, the 2 Skinnee J's.

http://www.somethingwithanh.com/mp3/...eejs_pluto.mp3

Pluto

With depravity,
I break lots of gravity
Blast past the atmosphere
to the last frontier
I go boldly through space and time
The sky's the limit,
but they're limiting the sky
I break orbit by habit,
I ignite satellites and leave rings round the planets
A flying ace like that beagle,
nevertheless this alien remains illegal
Cause their discovery dont cover me
the immigrants been left in the cold
to grow old
and disintegrate
Discriminate
against the distant and disclaimers,
Cause small minds can't see past Uranus
When I shun their race
cause that's just a phase
and my odyssey runs in 2001 ways
And I can see clearly now like Hubble
shoved off the shuttle,
here's my rebuttal
It's a planet.

Who do you represent?
I represent the smallest planet
A tourney in this journey
versus those who tried to ban it.
If you don't agree
go see interplanet Janet Cause
the sun is star like
Pluto
is planet.
So lend me all ears
and let me state my case,
about all the types of satellites we must embrace
Cause like parents'
great-grandparents,
this planet was an immigrant,
to deport its an offense.
It's an upstanding member of the solar system
Abide the laws of Earth and make it a victim.
Of Proposition
107,
When Pluto spawns a moon it will apply to the heavens.
A dandy like Judas of a chariot
If you demote this boat
remote to a goat
It's like taking ETs custody from Elliot,
support yours
clearly put cause,
simply put

Pluto is a planet. Pluto!
Pluto is a planet. Pluto!
(Do it for the children, if not for yourself)
Pluto is a planet. Pluto!
(Do it for the children, if not for yourself)
Pluto is a planet.

Somewhere this year a heated debate will take place in science class with an ill informed teacher resulting in an unjust detention.

And Hollywood will make a movie of it starring Dakota Fanning.