New moon discovered at Pluto

[YellowSubmarine]

And what is a planet? A free floating body in space that is spherical, and does not orbit any other body. What is a dwarf planet? A really tiny planet which shares its orbital space with one or more larger planets and/or asteroids.

See, the definition already confused you. You're saying that there are no language problems, yet you fail to use the term properly yourself.

A dwarf planet is not a really tiny planet because it's not a planet. A dwarf planet is not a planet. Period. It's something different, distinct. At least that's what IAU think it is. Well, I happen to disagree, and I don't think I'm alone on that.

If tomorrow morning we discovered another large planet circling the sun on a path that regularly crosses Earth's orbit, then EARTH would be a dwarf planet by that definition.

So much for "dwarf" denoting size I guess! Ah well, that's not such a big deal. But what you say is very much true – Earth was probably not a planet when life appeared on it. Go figure.

 

[iguana_tonante]

The thing has 4 moons and still those IAU bastards don't believe it's a planet...

Pluto is a planet, and I refuse to accept otherwise.

I'll make sure to relay your complaints to the astronomical community. I think they will be devastated.

 

[Crazy Eddie]

And what is a planet? A free floating body in space that is spherical, and does not orbit any other body. What is a dwarf planet? A really tiny planet which shares its orbital space with one or more larger planets and/or asteroids.

See, the definition already confused you. You're saying that there are no language problems, yet you fail to use the term properly yourself.

That IS the proper use, according to the IAU. Take it up with them if you disagree.

A dwarf planet is not a really tiny planet because it's not a planet.

Yes it is. In exactly the same way that a dwarf star (.e.g. the Sun) is still a star. There are only two kinds of people who claim this means pluto is "not a planet": Science-channel attention whores speaking primarily in sarcasm, and newspaper/magazine science writers who don't know asteroids from aspercreme.

A dwarf planet is not a planet. Period. It's something different, distinct.

To the extent that any two types of celestial objects can be said to be distinct, sure.

So much for "dwarf" denoting size I guess!

It was never supposed to, except insofar as a "planet" must be a spherical body and that can only occur above a certain size. In Pluto's case, the new definition arose from the fact that pluto shares its orbit with a number of other similar-sized objects and quite a few larger ones, notably the planet Neptune.

 

[Saquist]

Amazing how emotional and defiant people can be over the status of an ice ball that's about 4 billion miles away.

As a planet, Pluto was the least of them. As a Kuiper belt object, it's one of the most significant.

I think it's still planet.
Mass Effect still treats it as a planet...(so nah)

The outlines of what is planet don't make much sense when it comes to "clearly your orbit. Jupiter hasn't even completely cleared it's orbit and the only reason Pluto hasn't is because it's in the Kuiper belt where everything was pushed after ignition.

So if there was a large planet sitting in pluto's place it would still be dwarf planet because it hasn't cleared it's orbit. It's silly. Clearing an orbit has nothing to do with if you're small planet or large planet and that's the very stupid thing about their definition. They needed to come up for a mimum size for a Planet in order to define a dwarf planet.

 

[YellowSubmarine]

Yes it is. In exactly the same way that a dwarf star (.e.g. the Sun) is still a star. There are only two kinds of people who claim this means pluto is "not a planet": Science-channel attention whores speaking primarily in sarcasm, and newspaper/magazine science writers who don't know asteroids from aspercreme.

http://www.iau.org/public_press/news/detail/iau0603/

 

[SPCTRE]

Please don't tell me that me posting a silly picture started this debate all over again.

Actually, please tell me that it did

 

[iguana_tonante]

Of course it did. Some people are just unable to let it go.

 

[Ensign_Redshirt]

In my personal canon, Pluto's a planet. j/k

 

[Pavonis]

The outlines of what is planet don't make much sense when it comes to "clearly your orbit. Jupiter hasn't even completely cleared it's orbit and the only reason Pluto hasn't is because it's in the Kuiper belt where everything was pushed after ignition.

No, Jupiter has cleared its orbit, and dominates it. If you're referring to the Trojan asteroids, they're caught at Jupiter's Lagrange points. If that doesn't indicate that Jupiter has cleared and now controls the space it orbits through, then the incredible size difference between the Trojans and Jupiter ought to suggest that Jupiter is the planet.

Pluto, though, is just another iceball out there. It's not alone, and it's not controlling the orbits of any objects sharing the orbit. It's not even necessarily the biggest iceball out there! The only thing notable about Pluto is that it was the first one found.

So if there was a large planet sitting in pluto's place it would still be dwarf planet because it hasn't cleared it's orbit. It's silly. Clearing an orbit has nothing to do with if you're small planet or large planet and that's the very stupid thing about their definition. They needed to come up for a mimum size for a Planet in order to define a dwarf planet.

What's so special about a minimum size, though? Mass, and therefore gravity, are the important parameters through which other objects' orbits are affected. Pluto clearly doesn't have enough mass, despite being round, to control the orbits of everything in the space through which it orbits the Sun.

Basically, and to be a bit crude, Pluto didn't kick the ass of every other object out there, so it's not a planet. Jupiter did kick the ass of every object near it, and then made them its bitches, so it is a planet.

What I don't understand is why some people are so emotionally invested in the definition of Pluto's status. Science isn't a democratic process, and the IAU isn't beholden to the public to create a definition that is popular.

 

[Saquist]

No, Jupiter has cleared its orbit, and dominates it. If you're referring to the Trojan asteroids, they're caught at Jupiter's Lagrange points. If that doesn't indicate that Jupiter has cleared and now controls the space it orbits through, then the incredible size difference between the Trojans and Jupiter ought to suggest that Jupiter is the planet.

Sounds like a technicality.

Pluto, though, is just another iceball out there. It's not alone, and it's not controlling the orbits of any objects sharing the orbit. It's not even necessarily the biggest iceball out there! The only thing notable about Pluto is that it was the first one found.

What's so special about a minimum size, though? Mass, and therefore gravity, are the important parameters through which other objects' orbits are affected. Pluto clearly doesn't have enough mass, despite being round, to control the orbits of everything in the space through which it orbits the Sun.

Basically, and to be a bit crude, Pluto didn't kick the ass of every other object out there, so it's not a planet. Jupiter did kick the ass of every object near it, and then made them its bitches, so it is a planet.

What I don't understand is why some people are so emotionally invested in the definition of Pluto's status. Science isn't a democratic process, and the IAU isn't beholden to the public to create a definition that is popular.

... like I said...that doesn't define dwarf either.
Dominating an orbit means nothing to size if you're in a debris field.

 

[YellowSubmarine]

What I don't understand is why some people are so emotionally invested in the definition of Pluto's status. Science isn't a democratic process, and the IAU isn't beholden to the public to create a definition that is popular.

Because the definition is sloppy:
1. It says “cleared its neighbourhood” instead of “gravitationally dominant”, so you can read it as if Jupiter is a dwarf planet. Also a variation of “gravitationally dominant” could make it easier to judge the class of an extrasolar object, and could also solve a bunch of the other problems listed below – it's easier to improve compared to the other one.
2. It says “in orbit around the Sun”, automatically excluding extrasolar planets. It could have said, dunno, in orbit around a star? Most planets in the universe don't orbit the Sun. I think.
3. “Dwarf planet” is linguistically unsound. “Dwarf planetoid” or simply “planetoid” would have been a lot better.
4. “Dwarf” means tiny, whereas the definition is not so much about size as it is about orbital characteristics, which in turn leads to the next two bizarre issues:
* The definition seems to imply the existence of gas giant dwarf planets, I kid you not.
* The definition means that the Earth was first a proto-planet, then a dwarf planet and then a planet.

Pluto is the least of the troubles. What's funny is that the current definition was made in order to make Pluto not a planet, when I can't see a particularly good reason to do so – it has the same physical characteristics as a terrestrial planet, it orbits a star, in the habitable zone it could harbour a civilization (not that we know that an asteroid couldn't), etc.

Terrestrial planets and dwarf planets are as close as you can get, they are closer than a terrestrial planet and a gas giant planet are. That's why in jest I suggested excluding the Earth, Venus, Mercury and Mars from the definition of a planet.

 

[SPCTRE]

In my personal canon, Pluto's a planet. j/k

 

[Saquist]

What I don't understand is why some people are so emotionally invested in the definition of Pluto's status. Science isn't a democratic process, and the IAU isn't beholden to the public to create a definition that is popular.

Because the definition is sloppy:
1. It says “cleared its neighbourhood” instead of “gravitationally dominant”, so you can read it as if Jupiter is a dwarf planet. Also a variation of the latter would make it easier to judge the class of an extrasolar object, and would also solve a bunch of the other problems listed below.
2. It says “in orbit around the Sun”, automatically excluding extrasolar planets. It could have said, dunno, in orbit around a star? Most planets in the universe don't orbit the Sun. I think.
3. “Dwarf planet” is linguistically unsound. “Dwarf planetoid” or simply “planetoid” would have been a lot better.
4. “Dwarf” means tiny, whereas the definition is not so much about size as it is about orbital characteristics, which in turn leads to the next two bizarre issues:
* The definition seems to imply the existence of gas giant dwarf planets, I kid you not.
* The definition means that the Earth was first a proto-planet, then a dwarf planet and then a planet.

Pluto is the least of the troubles.

Number two is a REALLY good point

 

[Python Trek]

A "dwarf planet" is a planet. There's a modifier, "dwarf", and a noun, "planet". Scientists may be good at math and stuff, but they suck at grammar.

 

[Saquist]

Note: Don't use scientist to draw up a legal contract or any legislature....

 

[Pavonis]

Dominating an orbit means nothing to size if you're in a debris field.

There wouldn't be a debris field if the object was dominating the orbit.

Note: Don't use scientist to draw up a legal contract or any legislature....

And don't use an artist to conduct scientific research. Or a lawyer to perform brain surgery. Any other non sequiturs?

Because the definition is sloppy:
1. It says “cleared its neighbourhood” instead of “gravitationally dominant”, so you can read it as if Jupiter is a dwarf planet. Also a variation of “gravitationally dominant” could make it easier to judge the class of an extrasolar object, and could also solve a bunch of the other problems listed below – it's easier to improve compared to the other one.

The degree of "neighborhood clearance" is quantifiable. It's not arbitrary. The ratio of planet mass to remaining debris mass can be parameterized, and a cutoff value can be selected for the definition.

3. “Dwarf planet” is linguistically unsound. “Dwarf planetoid” or simply “planetoid” would have been a lot better.

What's wrong with adjectives?

4. “Dwarf” means tiny, whereas the definition is not so much about size as it is about orbital characteristics, which in turn leads to the next two bizarre issues:
* The definition seems to imply the existence of gas giant dwarf planets, I kid you not.
* The definition means that the Earth was first a proto-planet, then a dwarf planet and then a planet.

Tiny is relative. Red dwarf stars are small compared to other stars, but huge compared to planets, or to you, or to bacteria.

As for your example of gas giant exoplanets sharing an orbit, I doubt that's a stable arrangement over billions of years. One of them may end up "kicking the ass" of the other. At any rate, young systems with objects that are still sorting out their orbital equilibria shouldn't be required to fit orderly definitions.

Pluto is the least of the troubles. What's funny is that the current definition was made in order to make Pluto not a planet, when I can't see a particularly good reason to do so – it has the same physical characteristics as a terrestrial planet, it orbits a star, in the habitable zone it could harbour a civilization (not that we know that an asteroid couldn't), etc.

The problem was the Pluto was clearly not the only object out there, that there were many similar objects out there, and that calling Pluto a planet but not calling Eris one, or any other similar object out there a planet, was arbitrary. If the classification of objects comes off as arbitrary, too, well that's because reality just isn't tidy.

Not everything that orbits a star can fall into a discrete category easily. As a scientist, all I can tell you is that we do our best to lay out orderly classifications for things (planets, species, etc), but sometimes the definitions aren't perfect. Some of that is the fault of language in general. Should new words be coined for all the different types of objects that orbit stars? Maybe.

 

[YellowSubmarine]

What's wrong with adjectives?

Nothing, but when “dwarf” is used as an adjective, the compound term is supposed to be a subset of the general term. But dwarf planets are not a subset of planets.

At any rate, young systems with objects that are still sorting out their orbital equilibria shouldn't be required to fit orderly definitions.

Yeah, I admit that it's a disingenuous example, but we don't know which orbital configurations are actually stable. I do believe that double planets are stable. Some gas giants on extremely distant orbits won't clear their neighbourhoods too.

Should new words be coined for all the different types of objects that orbit stars? Maybe.

Yes planets! I want a word to describe planet-like objects such as gas giants, terrestrial planets, dwarf planets and spherical moons.

 

[Pavonis]

What you believe isn't relevant. Orbits are Newtonian, so they're calculable over long timescales. Your example planetary system isn't stable according to the article you cited.

As for giving a name to everything that orbits stars, why not just call it "stuff"?

 

[Mr. Laser Beam]

As for giving a name to everything that orbits stars, why not just call it "stuff"?

George Carlin and I both agree with this.

 

[YellowSubmarine]

Orbits are Newtonian, so they're calculable over long timescales.

Um, yes, but we can't brute-force all possible configurations, we only know if a given configuration is stable or not, and as far as I know systems with more than two bodies are very difficult to work with if you don't narrow the parameters. The possibility for stable configurations is not excluded, and I'm almost certain that double planets are stable (since double stars, double dwarf planets can be stable, I reckon that it must be true for planets too)