Pluto is was and always will be a planet

[Ziggurat]

Where did you explain why it's meaningless?

Do a search of this thread. You are the only person who has used this word.

I honestly don't think it'd be hard for you to do. You just have to move beyond how things "feel".

Pointing out that something can cause confusion isn't a matter of feelings.

 

[Belz...]

Do a search of this thread. You are the only person who has used this word.

Woah, sorry. I meant "misleading". That's quite a typo, there

Pointing out that something can cause confusion isn't a matter of feelings.

But that it can cause confusion is a truism. That's true of literally any definition. I'm asking you to do more than just say "well, it shouldn't be like this". Why is it so hard?

 

[Ziggurat]

Woah, sorry. I meant "misleading". That's quite a typo, there

Calling a planet like Jupiter a "dwarf planet" is misleading because the name suggests that it's small, but it's not. Is that really not obvious to you? We've been over this already.

But that it can cause confusion is a truism. That's true of literally any definition.

But it's less true of some definitions than of others.

I'm asking you to do more than just say "well, it shouldn't be like this". Why is it so hard?

I already have done more than that.

 

[Belz...]

Calling a planet like Jupiter a "dwarf planet" is misleading because the name suggests that it's small, but it's not. Is that really not obvious to you? We've been over this already.

Yeah but the only problem is the name, not the classification. Change it to "planetoid" or "swatzherhaalt" and the problem goes away.

But it's less true of some definitions than of others.

Sure, I'd buy that.

I already have done more than that.

Well, I don't agree. I think that your suggestion for defining a planet is passable, but results in a large number of "planets" for the solar system, a number that will only grow with time. I think that your dislike for the "clearing the neighborhood" criterion is based on how it excludes Pluto rather than any pragmatic consideration.

All my attempts to have the discussion break beyond how things feel have failed, unfortunately. I'd really have liked us to find some common ground to discuss this. Clearly, astronomers would rather have an added layer of categorisation, and if we're to ditch the aforementioned criterion we'd need to replace it with one that's either less confusing, to use your own words, or more useful, to use mine.

 

[theprestige]

Seems like "spheroid under its own gravity" and "orbits a star" are all you need for an intuitive, historically-consistent definition. What's the problem with just using that?

 

[Ziggurat]

Yeah but the only problem is the name, not the classification. Change it to "planetoid" or "swatzherhaalt" and the problem goes away.

The name is the classification. And "planetoid" would indeed reproduce the problem, since it also implies something smaller than a planet. "Swatzherhaalt" would not cause that problem, but it would produce others.

Well, I don't agree. I think that your suggestion for defining a planet is passable, but results in a large number of "planets" for the solar system, a number that will only grow with time.

Yes, it would. Not once have you explained why this is a problem or a drawback.

I think that your dislike for the "clearing the neighborhood" criterion is based on how it excludes Pluto rather than any pragmatic consideration.

That is not true. I have specifically outlined why I think it's a problem based on other reasoning.

All my attempts to have the discussion break beyond how things feel have failed, unfortunately.

Your attempts have been weak, to put it charitably. When I point out that the cleared neighborhood definition can lead to confusion, you simply ignore it or pretend that it's a matter of feeling.

I'd really have liked us to find some common ground to discuss this. Clearly, astronomers would rather have an added layer of categorisation, and if we're to ditch the aforementioned criterion we'd need to replace it with one that's either less confusing, to use your own words, or more useful, to use mine.

It's easy to add sub-categories to the category of planet. For example, gas giants, rocky planets, icy planets. You could even add dwarf planets as a sub-category. And these sub-categories don't even all have to be mutually exclusive, it's OK to have overlapping sub-categories.

I have an additional suggestion along those lines: icy dwarf planet. Put the threshold at the minimum mass a non-spinning rocky body would need in order for gravity to shape it hydrostatically. If an object is below that mass, then it won't achieve hydrostatic equilibrium if it's rocky, but it might if it's icy. This allows for non-dwarf icy planets, if they're big enough, but gives you a category for the small icy planets that wouldn't even be planets if they were rocky. Hell, you could even split planets and dwarf planets as separate mutually exclusive categories at this mass if you wanted. It would still be an improvement over the current definition.

 

[theprestige]

All my attempts to have the discussion break beyond how things feel have failed, unfortunately.

I don't see how the discussion can possibly move beyond how things feel. "Planet" is essentially a literary classification.

I'd really have liked us to find some common ground to discuss this. Clearly, astronomers would rather have an added layer of categorisation, and if we're to ditch the aforementioned criterion we'd need to replace it with one that's either less confusing, to use your own words, or more useful, to use mine.

Astronomers have feelings about the classification. You have feelings about replacing it. Ziggurat has feelings about replacing it.

But how about this? Instead of arguing with Ziggurat about his feelings, why not just state in your own terms the non-feelings-based common ground you have in mind? Maybe people will discuss your idea, maybe they won't. But at least you'll be presenting your idea as such, without depending on Ziggurat to follow your lead.

 

[Belz...]

The name is the classification. And "planetoid" would indeed reproduce the problem, since it also implies something smaller than a planet.

I don't think that it does. "Planetoid" means "like a planet", not "small planet". After all, "humanoid" doesn't mean "small human".

"Swatzherhaalt" would not cause that problem, but it would produce others.

I kind of like the sound of it, but I can propose more if you want!

Yes, it would. Not once have you explained why this is a problem or a drawback.

I have, actually. I've explained that when you have a crapton of things in a category, we usually subdivide it because it makes it easier to work with.

That is not true. I have specifically outlined why I think it's a problem based on other reasoning.

Ok then, aside from what it should be, or that it's misleading or confusing or whatever, which are all about how it feels, what reasoning have you proposed?

When I point out that the cleared neighborhood definition can lead to confusion, you simply ignore it or pretend that it's a matter of feeling.

I'm trying to pin you down on something more specific. As I said, a LOT of words lead to confusion, but we still use them. Hell, "planet" is often confusing, and you're not proposing we drop the word altogether.

It's easy to add sub-categories to the category of planet. For example, gas giants, rocky planets, icy planets. You could even add dwarf planets as a sub-category. And these sub-categories don't even all have to be mutually exclusive, it's OK to have overlapping sub-categories.

Agreed.

I have an additional suggestion along those lines: icy dwarf planet. Put the threshold at the minimum mass a non-spinning rocky body would need in order for gravity to shape it hydrostatically. If an object is below that mass, then it won't achieve hydrostatic equilibrium if it's rocky, but it might if it's icy. This allows for non-dwarf icy planets, if they're big enough, but gives you a category for the small icy planets that wouldn't even be planets if they were rocky. Hell, you could even split planets and dwarf planets as separate mutually exclusive categories at this mass if you wanted. It would still be an improvement over the current definition.

Ok so how about "major planet" and "minor planet" or something along those lines?

 

[Molinaro]

While this might be regarded as a fun thread, scientific input would be appreciated. I thought the relegation was a disgrace at the time, but New Horizon laid proof like an EGG.

Your use of the word 'disgrace' is what turns this from a scientific discussion to an emotional one. And that necessarily opens up the possibility that some will find such an emotional reaction to be comical.

 

[Ziggurat]

I don't think that it does. "Planetoid" means "like a planet", not "small planet". After all, "humanoid" doesn't mean "small human".

Except that the number of factors which can disqualify something that is like a planet from actually being a planet are much more limited. A moon can be like a planet but not a planet, but we've already got a name for those, so they shouldn't be planetoids. An object can be like a planet but too big to be a planet, in which case it turns into a brown dwarf, so that's not a planetoid either. If you take the IAU's definition, then it could be like a planet except it hasn't cleared its neighborhood. That's a case where the term might work, but nobody seems to like that criteria, and if we discard it (as I hope we do), then that's not a case where the term would be used. Which pretty much just leaves us with an object being too small, like Vesta.

I have, actually. I've explained that when you have a crapton of things in a category, we usually subdivide it because it makes it easier to work with.

But subdivision is easy in this case.

Ok then, aside from what it should be, or that it's misleading or confusing or whatever, which are all about how it feels

If you want to say that trying to avoid confusion is just about feels, then any possible motive you can have for doing anything is just about feels, including not wanting to overload a category with members in order to make it easier to work with.

Ok so how about "major planet" and "minor planet" or something along those lines?

Sure, such a division would be easy and practical, as long as the difference is something sensible like mass or size.

 

[Belz...]

Except that the number of factors which can disqualify something that is like a planet from actually being a planet are much more limited. A moon can be like a planet but not a planet, but we've already got a name for those, so they shouldn't be planetoids.

No, no. I meant bodies that orbit the sun, have hydrostatic equilibrium, but don't meet the other requirements, whatever they may be. Essentially replacing the word "dwarf planet" with something else.

If you want to say that trying to avoid confusion is just about feels, then any possible motive you can have for doing anything is just about feels, including not wanting to overload a category with members in order to make it easier to work with.

That's not my point. My point is demonstrating that it's confusing to more than just you or me. Is it confusing for astronomers? They're the ones dealing with these terms on a daily basis.

Sure, such a division would be easy and practical, as long as the difference is something sensible like mass or size.

See, I knew we could agree on something.

 

[Ziggurat]

That's not my point. My point is demonstrating that it's confusing to more than just you or me. Is it confusing for astronomers? They're the ones dealing with these terms on a daily basis.

Primary school educators have to deal with the term "planet" a lot as well. And I think it would be beneficial if they were using the terms the same way. That's not always possible in science (temperature is an example: the actual definition is much more subtle than the popular definition, and must be so by necessity), but I think it is possible here.

 

[Red Baron Farms]

Ok so how about "major planet" and "minor planet" or something along those lines?

Now you are back to planets and dwarf planets both being planets.

Pluto is was and always will be a planet

 

[ahhell]

Anyone that knows about the Kuiper Belt that thinks Pluto is a planet is leaving in a fantasy solar system full of rainbow farting unicorns.

I figured out pluto wasn't a planet 20 years ago.

Pluto is not, never was, and never will be a planet.

 

[Elagabalus]

...Essentially replacing the word "dwarf planet" with something else...

"Aplanet"?

 

[Belz...]

Primary school educators have to deal with the term "planet" a lot as well. And I think it would be beneficial if they were using the terms the same way. That's not always possible in science (temperature is an example: the actual definition is much more subtle than the popular definition, and must be so by necessity), but I think it is possible here.

That's fair.

Personally, and again I'm not an astronomer, I find the word "dwarf planet" confusing specifically because it seems to indicate that it's a type of planet when it's not. Also, as discussed earlier I dislike the 'clearing the neighborhood' criterion, but aside from the fact that I find it confusing for myself, it's actually pretty hard to determine, and there's also the issue of the trojans.

So I agree that hydrostatic equilibrium and primary orbit around a star should be the main criteria, if only because it's how the word's been understood for centuries. However, in order to keep the number of planets down, and since we seem to agree that primary school teachers and students have to deal with the list also, I'd split between major planets and minor planets (or planets and planetoids, as per my previous suggestion), with the difference being based on mass (which will necessarily be arbitrary but could be around 1/20th earth masses, for instance) and orbital characteristics (there are important differences of size, mass, composition and orbit between the Kuiper belt bodies, whose orbits look like something drawn by a madman, and those more massive ones that are relatively close to the sun and in near-circular motions.).

 

[Belz...]

Now you are back to planets and dwarf planets both being planets.

Yes, I'm discussing a compromise. I know, I know, that's heresy on the internet.

Personally I'd just call the non-major ones "planetoids" or something to that effect: they are like planets but not planets, while the irregularily-shaped bodies would just be asteroids.

 

[Ziggurat]

However, in order to keep the number of planets down, and since we seem to agree that primary school teachers and students have to deal with the list also, I'd split between major planets and minor planets, with the difference being based on mass (which will necessarily be arbitrary but could be around 1/20th earth masses, for instance) and orbital characteristics (there are important differences of size, mass, composition and orbit between the small, icy bodies whose orbits look like something drawn by a madman, and those more massive ones that are relatively close to the sun and in near-circular motions.).

Mass or size is better than orbital characteristics like eccentricity, because it makes for smoother extension to other solar systems, where very large planets might have high eccentricities or small planets could have small eccentricities. Mass is probably better than size because it's usually easier to measure, at least within our solar system.

 

[Belz...]

Mass or size is better than orbital characteristics like eccentricity, because it makes for smoother extension to other solar systems, where very large planets might have high eccentricities or small planets could have small eccentricities. Mass is probably better than size because it's usually easier to measure, at least within our solar system.

Yes, you're right. It's biased towards our own solar system.

But then, we don't know how other systems are built. Maybe planets their stars are pretty much always in a near-circular orbit and this wouldn't be a problem. For now it's the only system for which we have reliable data.

 

[Ziggurat]

Yes, you're right. It's biased towards our own solar system.

But then, we don't know how other systems are built. Maybe planets their stars are pretty much always in a near-circular orbit and this wouldn't be a problem. For now it's the only system for which we have reliable data.

Our data is limited and we don't know how representative it is, but there are a lot of exoplanets with eccentricities larger than Haumea (0.19), Makemake (0.15), Pluto (0.25), and even Eris (0.44), and even a few that exceed the eccentricity of Sedna (0.85). At the extreme end, the exoplanet HD 20782 b has an eccentricity of 0.97 and an estimated mass of 1.8 Jupiters. We can't extrapolate reliable statistics about exoplanet eccentricities because of the possibility of sampling bias, but there are certainly at least some cases of large planets with high eccentricities out there.

ETA: Runner up for extreme exoplanet eccentricity goes to HD 80606 b, which has an eccentricity of 0.93 and a mass of 4 Jupiters.