Pluto's Not A Planet Anymore

Off Topic
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http://news.yahoo.com/s/ap/20060824/ap_on_sc/planet_mutiny_9

WTF? Can they do that?

[i]"For now, membership will be restricted to the eight “classical” planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Much-maligned Pluto doesn’t make the grade under the new rules for a planet: “a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a … nearly round shape, and has cleared the neighborhood around its orbit.”

Pluto is automatically disqualified because its oblong orbit overlaps with Neptune’s."[/i]

Damn. Chalk that up as one more thing I learned in grade school that the next generations won’t be learning. Feels kinda weird now. What about the pneumonic for remembering the planets “My Very Excited Mother Just Served Us Nine Pies.” More useless knowledge, I guess.

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[quote]Minotaur wrote:
http://news.yahoo.com/s/ap/20060824/ap_on_sc/planet_mutiny_9

WTF? Can they do that?
[/quote]

They can and just did. It’s not like Pluto will break free of its orbit and become a doomsday asteroid careening towards our planet out for vengeance… although that would be wicked cool.

But in reality, Pluto is more of a huge asteroid than a true planet. I knew the demotion would happen, it was just a matter of when. In the mid-1800’s, Ceres, the largest asteroid in the belt, was a “planet”, too.

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Pluto would cease to be a planet anyways. And not just by definition. One of these millenia, Neptune will smack into Pluto and its moon (Charon), absorbing them both, right? So fuck Pluto! Just wait a while, and see if you still think it’s a planet :slight_smile:

Doesn’t it make more sense anyways, that the planets nearer the sun are solid, and those farther out are gas giants? (gravity and density)

Too bad “science” didn’t declare this before. Pluto just doesn’t make any sense as a planet.

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What about zena and sidna, are they planets now?

Spending too much time at the observatory with my kid.

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Probably a stupid question, but how come landing on Jupiter by a satellite has never been attempted? They don’t have a surface or what? Do we know?

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[quote]muscleshark wrote:
Probably a stupid question, but how come landing on Jupiter by a satellite has never been attempted? They don’t have a surface or what? Do we know?[/quote]

My guess is it’s too far, Mars is about 35 million miles, and Jupiter is over 370 million miles away from earth.

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This is honestly the most interesting thread ever!

As to why landing on Jupiter has never been attempted: I believe (and I could be way off here) that it is due in-part to the fact that Jupiter has such tremendous gravity that most anything we could send there would be crushed by it. That and the sheer distance.

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[quote]muscleshark wrote:
Probably a stupid question, but how come landing on Jupiter by a satellite has never been attempted? They don’t have a surface or what? Do we know?[/quote]

Galileo dropped a probe. Jupiter’s atmosphere is so dense and hot that nothing could possibly survive “landing” on what is theorized to be a ocean of liquid helium, simple hydrocarbons and methane. The probe lasted about three minutes if I remember correctly before the heat shield failed and it was burned up or crushed.

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[quote]Minotaur quoted:
“Pluto is automatically disqualified because its oblong orbit overlaps with Neptune’s.”[/quote]

So why isn’t Neptune similarly disqualified? It isn’t like Neptune kicked Pluto out of the neighborhood, either.

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[quote]thomas.galvin wrote:
Minotaur quoted:
“Pluto is automatically disqualified because its oblong orbit overlaps with Neptune’s.”

So why isn’t Neptune similarly disqualified? It isn’t like Neptune kicked Pluto out of the neighborhood, either.[/quote]

Because Neptune’s orbit is much less ellipical than Pluto’s. Because Neptune is a gas giant many thousands of times Pluto’s mass. Because Neptune fits every classical definition of a planet (however arbitrary those definitions may be).

And finally, if you accept Pluto as a planet, every Kuiper belt object and possibly every Oort cloud object larger than Pluto would have to be called a planet, as well. A thousand “planet” solar system is rather unwieldy, don’t you think?

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Pluto will always be a planet as far as I’m concerend.

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[quote]Crispyknight wrote:
thomas.galvin wrote:
So why isn’t Neptune similarly disqualified? It isn’t like Neptune kicked Pluto out of the neighborhood, either.

Because Neptune’s orbit is much less ellipical than Pluto’s. Because Neptune is a gas giant many thousands of times Pluto’s mass. Because Neptune fits every classical definition of a planet (however arbitrary those definitions may be).

And finally, if you accept Pluto as a planet, every Kuiper belt object and possibly every Oort cloud object larger than Pluto would have to be called a planet, as well. A thousand “planet” solar system is rather unwieldy, don’t you think?[/quote]

I agree that Pluto shouldn’t be considered a planet, but I also think this definition sucks.

“A celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a … nearly round shape, and has cleared the neighborhood around its orbit.” There is no mention of the shape of the solar orbit, nor of size. In fact, this new definition was drawn up, in part, to avoid making an arbitrary size limit.

If Pluto fails to meet the requirement of a planet under this definition, so does Neptune. If “it has a more circular orbit” or “its really friggin big” are the reasons Neptune is still considered a planet, add them to the definition. Don’t just make arbitrary exceptions to the rule.

As an aside, I don’t mean you, personally, but the IAU.

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[quote]Crispyknight wrote:
Because Neptune’s orbit is much less ellipical than Pluto’s. Because Neptune is a gas giant many thousands of times Pluto’s mass. Because Neptune fits every classical definition of a planet (however arbitrary those definitions may be).[/quote]

It’s not just the ellipticity of Pluto’s orbit (which is only 25% greater than Mercury’s, for example), but its inclination, too. Pluto’s orbit is inclined 17.15deg with respect to the ecliptic (the imaginary plane of the Solar System which cuts through the Sun’s equator).

Its eccentric orbit takes it inside Neptune’s orbit twice every plutonian year (248.54 Earth years), for example, during Jan 1979 – Feb 1999.

Pluto is locked in a 3:2 resonance with Neptune (which means it’s orbital period is 1.5 times that of Neptune), but both planets cannot meet. It is not true (contrary to what somebody posted further up) that Pluto (and its moon, Charon) will collide with Neptune at some point in the future.

Due to all these orbital peculiarities, it is very likely that Pluto and Charon were captured by the solar system at some point in the distant past, and were not formed like the other 8 planets.

Yes, that’s the case, although we don’t know if 1000 is an exageration, or an underestimate. Already, 2003UB313, an object discovered at about twice the distance from the Sun as Pluto, is twice its size too, so who knows how many more could be out there.

Under the new classification scheme, 2003UB313 would be called a “dwarf planet”.

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[quote]Todd23 wrote:
Pluto will always be a planet as far as I’m concerend.[/quote]

The solar system will always be geocentric, as far as I’m concerned. :stuck_out_tongue_winking_eye:

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[quote]thomas.galvin wrote:
I agree that Pluto shouldn’t be considered a planet, but I also think this definition sucks.

“A celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a … nearly round shape, and has cleared the neighborhood around its orbit.” There is no mention of the shape of the solar orbit, nor of size.[/quote]

The shape matters little; it’s going to be elliptical (no way out of that one) and its eccentricity doesn’t affect the fact that it’s in orbit around the Sun.

When you mention “size”, I assume you refer to the size of the object, not the size of the orbit. In this case, there is an implicit size limit, in the bit where they say “has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a … nearly round shape, and has cleared the neighborhood around its orbit”.

Although there is no fixed number value for the size, for an object to have enough gravity to make itself compact, roughly spherical, and capture any lost rocks around its orbit, it needs to be pretty big and massive (heavy).

You are probably correct :slight_smile: A very dense planet can fulfill all the above criteria at a smaller size than a less dense planet. As with men, size doesn’t matter (but mass does!).

Neptune has a pretty normal orbit (small eccentricity and inclination), is spherical, and has cleared up its path around the Sun, as evidenced by its 13 moons, the largest of which, Triton, is twice the size of Pluto. I think Neptune has earned its qualification :slight_smile:

Hopefully I’ve explained enough in my post that you no longer think Neptune is an exception!

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Another of the important pieces of the definition of a planet is it being a gravationally dominant object in its nearspace. Pluto does not fit this definition, while all eight classical planets do. Charon and Pluto form a binary planetoid system; the gravitational center of the two is outside of the body of Pluto. Thats a compelling reason to kick Pluto out of the group.

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[quote]muscleshark wrote:
Probably a stupid question, but how come landing on Jupiter by a satellite has never been attempted? They don’t have a surface or what? Do we know?[/quote]

The Solar System | StarDate Online

The mass is so large that the escape speed will be hard to reach.

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[quote]chewie wrote:
muscleshark wrote:
Probably a stupid question, but how come landing on Jupiter by a satellite has never been attempted? They don’t have a surface or what? Do we know?

The Solar System | StarDate Online

The mass is so large that the escape speed will be hard to reach.

[/quote]

Escape velocity is entirely irrelevant. By precedent, NASA has established that exploration probes (with few exceptions) do not return to Earth. All a probe would have to do is be able to land, not take back off.

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[quote]Todd23 wrote:
Pluto will always be a planet as far as I’m concerend.[/quote]

You know, it’s funny. My girlfriend was talking about this yesterday and how it probably related to when we were first told the earth was round. I’ve listened to so many people say, " You can’t do that! Pluto is a planet and that’s just the way it is!" I can just see people first being told the earth was round in disbelief just saying, " You can’t say that! The earth is flat and that’s just the way it is!"

Mike