12 planets in the Solar System will be official count on 24th of August

[Perfection]

I'll read this thread through ASAP, but on a side note: I don't think that the orbital eccentricity should be the most important criterion, but I'd keep it when talking about our own solar system. I mean that the term planet should have slightly different meaning when talking about our solar system, simply in order to appease the history, culture and finally, the astronomy.

Nah, I can do better then that. I can make it consistant inside the solar system and outside with my definition without any need of mentioning eccentricity. Besides, Mercury has variable eccentricity and can at times be more eccentric then many KBOs.

 

[Truronian]

I'm personally for the definition of a planet being a roughly spherical body orbitting the sun. This would give us a huge mess load of planets, of which the important ones are 1-8. I just think a simple definition is more useful than a ugly one.

 

[Lotus49]

The debate about what to call various celestial objects in the Solar system does not change anything, especially the confirmation that the human race is thinking way too small with regard to space discovery and exploration. Disappointing, yet again.

 

[GeoModder]

I wonder if it would help to include the composition of a "planet" in the definition. Most, if not all, of those KBO's would have less mass if they were formed and be located in the inner regions of the system. Typically about half or more of their mass is ice, of which quite a bit more would have been sublimated/evaporated/whatever if their orbit was within Jupiter's.

But that would leave Ceres as a planet, and the Earth/Moon system as a double planet in a couple of gigayears.

 

[Perfection]

I'm personally for the definition of a planet being a roughly spherical body orbitting the sun. This would give us a huge mess load of planets, of which the important ones are 1-8. I just think a simple definition is more useful than a ugly one.

My definition (see a few posts back) is relatively simple and avoids the ugly mess of having a bajillion feild objects as planets.

The debate about what to call various celestial objects in the Solar system does not change anything, especially the confirmation that the human race is thinking way too small with regard to space discovery and exploration. Disappointing, yet again.

Well this is sopposed to be a definition for extrasolars as well.

I wonder if it would help to include the composition of a "planet" in the definition. Most, if not all, of those KBO's would have less mass if they were formed and be located in the inner regions of the system. Typically about half or more of their mass is ice, of which quite a bit more would have been sublimated/evaporated/whatever if their orbit was within Jupiter's.

Well, a large enough iceball should be called a planet in my view. So I don't think composition should play an important factor. Ironically with the current IAU definition the iceballs get better treatment then the rocks. It takes a larger diameter and much more massive hunk of rock to form a ball then ice.

 

[Symphony D.]

I'd have to add my thoughts to the "this decision is just stupid" camp. After all the talk for years about dropping Pluto and relabeling it as a Kuiper Belt Object to get us down to 8 "planets" and a host of smaller bodies, they go in precisely the opposite direction. Charon? Oh please, it's a moon. Yes, it's the largest one relative to its parent, yes, they both orbit around a central gravitational point and are "twin worlds", but come on. And then Ceres? Why don't we just go define Europa, Ganymede, Io, Callisto, Titan, Triton, and so forth "planets" too? Hell, why not the Moon? It and Earth's shared gravitational axis is not the center of the Earth, it's somewhere in the Inner Mantle. How is that so radically different from being in space?

And then to include another Kuiper Belt Object... now everytime we find a new one we'll have to expand the number. What about the Oort Cloud? It's theorized there might be thousands of objects the size of Quaoar or Sedna out there.

I can't say I could immediately put forward a superior definition of what a "planet" is, however I must say the IAU's considered definition is not it.

 

[bhsup]

I am changing my position from my previous post.

The astronomers are the experts. We lowly serfs shouldn't be interfering in their ways. After all, it is "science" here, and they are the expert scientists. Our opinions should not count for anything since we're not the experts.

 

[Arcadian83]

I am changing my position from my previous post.

The astronomers are the experts. We lowly serfs shouldn't be interfering in their ways. After all, it is "science" here, and they are the expert scientists. Our opinions should not count for anything since we're not the experts.

I might agree with this stance, even though I think you are being sarcastic, if this were a technical or policy issue.

There are some aspects of science and engineering where an uninformed majority ruling over the experts could be calamatous. Remember the "National Do Not Email List" idea, off the top of my head.

The reason why I think our uninformed opinions matter in this case is because it is just a name, and just more political than technical of an issue. I suspect the 'experts' just want more mainstream attention in the news, in this case. The discovery of a 'new planet' is a bigger deal than a new asteroid or whatever.

 

[mdwh]

No, becuase it's based on qualitative behavior. What do all the 9 Planets but Pluto have in common? They're all masters of thier orbital domain. They herd small bodies from one place to another, they force them into belts and fields where there are no planets or into thier lagrange points. KBOs don't do this, neither to Asteroids.

But these are all arbitrary measures:
* How big does another body have to be before we say another body in the same orbit isn't master of its orbital domain? (E.g., Earth has other bodies in the same orbit, but they're very small.)
* How close do orbits have to be to be considered the same?
* How much do other orbits have to be affected to count as "herding"?
* How small are those "small bodies"?

I think it'd be a lot less complex and arbitrary to just choose a mass limit for a planet.

On the other hand, all these debates actually make me realise that the decision is a good one - when there are 200+ planets in the solar system, no one will be able to remember them all, and no one will thus care how many there are, and hence what the actual definition is. Does anyone know how many mountains there are, or do people argue whether a particular rocky region is a mountain or not?

 

[mdwh]

I'd have to add my thoughts to the "this decision is just stupid" camp. After all the talk for years about dropping Pluto and relabeling it as a Kuiper Belt Object to get us down to 8 "planets" and a host of smaller bodies, they go in precisely the opposite direction.

It's not opposite - plenty of people were already thinking of Xena as the 10th planet. If anything I think more people were expecting to gain rather than lose planets.

Charon? Oh please, it's a moon. Yes, it's the largest one relative to its parent, yes, they both orbit around a central gravitational point and are "twin worlds", but come on. And then Ceres? Why don't we just go define Europa, Ganymede, Io, Callisto, Titan, Triton, and so forth "planets" too? Hell, why not the Moon? It and Earth's shared gravitational axis is not the center of the Earth, it's somewhere in the Inner Mantle.

You misunderstand the definition. The definition is not about the centre of gravity not being at the centre of the planet - that will never be the case. It's about the centre being located in space.

Clearly with the moons of the gas giant, the centres of gravity are well within their planet, and that's the case with our moon too, I believe. For years people have suggested that Charon be a planet, so there's nothing new here either.

Is it a good definition? I don't know, but without it we have the problem of how to deal with twin systems where the bodies are of equal size - do we give the planet status to the one that's 10kg heavier, or what?

The only one surprising, in that I haven't heard people suggesting it be a planet (in recent times), is Ceres.

 

[I am the Future]

They cant just let this go. Saying that they should keep pluto for sake of tradition is unscientifically sound. Saying taht they cant add planets is equally unscientifically sound. The fact is taht as the world trys to base its ideas and oppinions more and moreon science a cultural definition for this just can not work. Just like a cultural definition for how people got here doesnt work. You wouldnt say that we should disregard evolution just because that is the way things have been or becuase it is just easier that way, would you?

 

[Perfection]

* How big does another body have to be before we say another body in the same orbit isn't master of its orbital domain? (E.g., Earth has other bodies in the same orbit, but they're very small.)

An object large enough to threaten the dominance of a planet will result in an unstable orbital situation resulting in significant disturbance of both bodies (collisions, ejections, large orbital changes)

* How close do orbits have to be to be considered the same?

I don't see how that is needed in my scheme

* How much do other orbits have to be affected to count as "herding"?

Planets effect the very area where small bodies are found and not found. For example, Pluto doesn't effect where they are or aren't not found to any significant degree but Earth does, it prevents a wide swath of space around 1AU from having a large amount of asteroids.

* How small are those "small bodies"?

Small enough to not have a significant orbital impact on any other body other then something crossing close by it.

 

[Sims2789]

I hope every non-captured asteroid doesn't become a planet, just as Phobos, Deimos, and scores of extra-Arean unspherical, minute chunks of rock somehow became moons.

The term "planet" is a layperson term; therefore, when there's a hundred planets in the Solar System, unless at least one is significant in size, I'll always consider there to be nine. My definition isn't scientific but that's why it's a layperson term.

As a general rule, I as a layperson will not use the term planet to describe Pluto-sized objects outside or inside of the Sol System; Pluto is an exception.

 

[Sims2789]

How is Charon a planet when Luna isn't? I believe Pluto/Charon and Earth/Moon orbit a common center of gravity (obviously closer to Earth and Pluto than the Moon and Charon) as opposed to orbiting a spot within the larger bodies. The definition of a planet that the IAU has adopted is "a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet." Therefore, since the Moon does not technically orbit Earth (if I'm right and the two orbit a common center of gravity), is it not a planet?

 

[Perfection]

How is Charon a planet when Luna isn't? I believe Pluto/Charon and Earth/Moon orbit a common center of gravity (obviously closer to Earth and Pluto than the Moon and Charon) as opposed to orbiting a spot within the larger bodies. The definition of a planet that the IAU has adopted is "a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet." Therefore, since the Moon does not technically orbit Earth (if I'm right and the two orbit a common center of gravity), is it not a planet?

The difference according to the IAU is because the Earth-Moon Barycenter is insdide Earth, while the Pluto-Cheron is outside Pluto

 

[Sims2789]

^I stand corrected. I thought the Barycenter (you've taught me a new word!) was between Earth and the Moon.

 

[Sims2789]

But... there's still nine planets! Every two-bit warlord in Somalia isn't a country by UN counts, even though they have a monopoly on force.

 

[Perfection]

But... there's still nine planets! Every two-bit warlord in Somalia isn't a country by UN counts, even though they have a monopoly on force.

Even though there's a newly-discovered world bigger then Pluto that orbits the sun directly?

 

[bhsup]

You know what? We need to take it down to 6 planets. Mercury, Venus, Earth, Mars, Uranus, Neptune.

Pluto? I'd be okay with keeping it, but if they refuse to be reasonable and just grandfather it, instead insisting that if Pluto stays then others have to become planets, then just chuck it and demote it to big ball near edge of solar system.

Jupiter and Saturn? New classification for such huge planets with their own independent systems. I know Jupiter and its satellites are also known as the Jovian System, but I am unaware of any such name for Saturn. Just what the new classification should be called, I've no idea. Maybe something like BFGG-1000, BFGG-2000, and so forth (big frakkin' gas giant 1, then it's satellites would be numbered 1001-1999....)

 

[Perfection]

Jupiter and Saturn? New classification for such huge planets with their own independent systems. I know Jupiter and its satellites are also known as the Jovian System, but I am unaware of any such name for Saturn. Just what the new classification should be called, I've no idea. Maybe something like BFGG-1000, BFGG-2000, and so forth (big frakkin' gas giant 1, then it's satellites would be numbered 1001-1999....)

Umm all gas giants (except Neptune, which lost a good deal of its moon structure catastophically) have good sized satelite systems. I really don't see why they shouldn't be planets. Moons shouldn't make planets not planets.