Correct, it’s called planet when it orbits arround the Sun AND has cleaned it’s orbit from asteroids, not the case of Pluto, whose orbit is still full of other objects, some even bigger than Pluto itself.
If it orbits an Planet instead of the Sun, it’s a Moon, even if it is bigger than some other planets.
I’ve often thought that ‘clearing’ it’s orbit is misleading. I believe the definition ought to be changed to ‘controls’ or ‘governs’ its orbit. This allows for objects in stable L4/L5 locations without inviting the caveats that ‘clearing’ needs.
Its because its a colloquial phrase that more or less the media picked up and ran with.
Actual astronomers and astrophysicists use math to describe what they’re talking about, math that you can find and learn fairly easily on wikipedia.
Lay people tend to just evaluate a phrase for its extremely literal meaning, not realizing that it is at best just pop science jargon, short hand to refer to a pretty well defined and precise concept, that is difficult to summarize without losing specificity.
There are many, many other examples of this kind of thing happening with other phrases or terms used to refer to complex concepts.
Jupiter has a permanent cloud of asteroids that follow it and neptune crosses the orbit of pluto so neither of those have cleared their orbits so of course they made exceptions so that their contrived definition fits.
Do you mean the asteroids at the Lagrangian points? Every single planet has asteroids there because math/physics dictates those points to be stable. Jupiter has the most at its points because it’s the largest planet.
Same with Neptune cleaning its orbit: It has collided with every single thing in its orbit EXCEPT those that synced their orbits to Neptune. An object that is gravitationally dominated by a single planet should not be a planet under any definition.
Sources because I had to read into your claims and I’m no astrophysicist:
Yes, that’s the made up exception. And for neptune not clearing its orbit due to pluto crossing that orbit? Well we have to make an exception for that so…um…the resonance between neptune and pluto. Exception achieved!
The rules are so contrived that it would not make sense for almost any other system except exactly ours. Whatever it takes to keep Earth’s category of “planet” important… you know… for reasons.
One person is navigating through a crowd, occasionally bumping into other people, having to juke and dodge their way around.
Another person has an entourage or body guards to their front, and two gaggles of papparazzi following behind them, at each 45 degree angle to their rear, as they walk through an entire empty street 4 lane street, with some occsional people walking past the whole scene on the sidewalk.
Pluto and Charon are basically an awkward, clumsy couple trying to get through a densely packed mall or convention.
Neptune is Taylor Swift, as an entire parade float, just, herself, body guards, papparazzi. And I guess she also can have some literal ingroup orbiters who manage to stick around, their lives revolve around her the same way their walking patterns do.
And then maybe, by chance, that awkward couple leaves the convention, gets lost, walks the wrong way to a restaurant, and end up just directly crossing the street that Swift walked down, 6 hours ago.
There, is that a sufficiently relatable visual metaphor to illustrate the difference between the two situations?
It’s a fine metaphor but it doesn’t work for scientific definitions which are exact. The IAU came up with the rule then had to make an exception to their own brand new rule in order to have Neptune remain a planet but not pluto even though both fail the rule. The exception is real and written down, not assumed.
Yet again another of the IAU rules is the body has to be assume hydrostatic equilibrium (nearly round). Mercury is NOT in hydrostatic equilibrium and they knew this. So they just…decided… that Mercury is a planet anyway and does not have to follow that rule.
So two planets don’t even follow the rules they made yet were unscientifically decided to be planets. Why? What was the point of it? Certainly wasn’t done for any scientific reason.
Ok, so, Pluto is more spherical than Mercury, but the most important criteria is local gravitational dominance.
Which Mercury has, but Pluto does not.
I do not see how this is a difficult concept to grasp.
Yeah, sometimes you can make a hasty definition, and then refine it to a level of consistent clarity, after it is justly critiqued, though that refined definition may be multi tiered and somewhat complex.
Thats… thats how science works, thats like the entire fundamental concept of it, right there, improving the level of detail to which you understand reality, via empiricism, logic, participatory debate.
The primary purpose of the planet defition refinenment is to emphasize the importance of relative local gravitational dominance.
I’m trying to imagine you using this kind of logic with like, biological taxonomy.
There is nothing difficult to grasp. They made rules then decided for no reason to let mercury break the rule. Why? Why not make mercury a dwarf planet instead of allowing it with no rule exception other than…just because.
This is not bioligical… those MUST follow the rules. This was a traditional unscientific list…
Exactly like constellations. Why not start removing stars from constellations because they are too far away? Except a couple of them just because.
This IAU conference vote was not unanimous… it was very contentious and many wanted a more geological and broad definition rather than an earth centered definition that literally ONLY applies to our solar system. “Planets” can only exist around OUR Sun. Think about that.
And for neptune not clearing its orbit due to pluto crossing that orbit?
Ah, yes. This is clearly justification for Pluto to become a planet! /s
If the only defense for your viewpoint is to throw out every definition and argument despite their validity, you aren’t arguing in good faith and have no facts to stand on
If the definition of a planet is that it has cleared is orbit then how is Neptune a planet? It shares its orbit with the dwarf planet pluto therefore they should both be dwarf planets correct?
As a consequence it does not then share its orbital region with other bodies of significant size, except for its own satellites, or other bodies governed by its own gravitational influence.
This latter restriction excludes objects whose orbits may cross but that will never collide with each other due to orbital resonance, such as Jupiter and its trojans, Earth and 3753 Cruithne, or Neptune and the plutinos.[3]
As to the extent of orbit clearing required, Jean-Luc Margot emphasises “a planet can never completely clear its orbital zone, because gravitational and radiative forces continually perturb the orbits of asteroids and comets into planet-crossing orbits” and states that the IAU did not intend the impossible standard of impeccable orbit clearing.
Pluto and other plutinos are bodies whose orbits are significantly governed by Neptune.
Go look at all the numerical values provided by various algorithms that measure essentially the extent to which a celestial body is locally gravitationally dominant, the extent to which it has ‘cleared its orbit’.
You may notice that everything considered a dwarf planet scores orders of magnitude less, by literally all the metrics, than actual planets.
I understand the exception created for Neptune. But they had to create this exception… for their own brand new rule… in order to classify 8 things. Notice the exception is written very specifically just to keep pluto from “clearing” is orbit.
Another IAU rule is that the body must assume hydrostatic equilibrium(nearly round). Mercury does NOT assume hydrostatic equilibrium. They knew this.
Guess what? They just…decided…Mercury doesn’t have to follow that rule.
It was all done very unscientifically.
Edit: I want to add that now there are only 8 planets…in the universe. There are no other planets because the definition includes that they must “orbit the Sun”. Not a star but very specifically the Sun. All this with exceptions for just 8 objects? I’m telling you it was a power trip thing more than a scientific endeavor.
What rules do you believe make for a definition that isn’t contrived? How do you exclude asteroids from your definition or reject other dwarf planets like Ceres without making up contrived exceptions of your own?
Planets are round, naturally formed bodies orbiting a star. (I know no planet is perfectly round and you can call any defined tolerance “contrived”, but at that point there are no useful and universally fitting definitions for anything in nature. Definitions are always categorizations by human standards)
Many asteroids are round. The list of planets, under your definition, would be so large it isn’t useful anymore. Even when Ceres, Pluto, and Eris were called planets the list was getting too long, and there are several larger than Ceres. Including every nominally round object would be insane.
Jupiter’s Trojan asteroids sit at Lagrange points. Material found there is not counted in the ‘clearing the orbit’ criteria. They are in stable orbits caused by the mass of the planet in question, not in lieu of a massive enough body.
Well of course that was the exception they had to come up with for their contrived rule. The exception is: “whatever it takes to make pluto not a planet”. Since the vote was agenda fueled and not a scientific discussion.
Once something new is discovered and breaks the rules they will have to modify the contrived rule to keep pluto not a planet.
Yes, that’s how science goes. Simple explanations and definitions often fall apart upon further discovery and require caveats that sometimes even reinforce the intention.
I agree except in this instance the goal was to keep Earth’s classification important. No other scientific objective. Just seemed very geocentric to me.
What is going to be funny is if/when they discover planet 9, and all the apparent Pluto superfans just utterly lose their shit when they attempt to comprehend that there can be another actual planet, and no, pluto still doesn’t count.
But how do we define what orbits what? On the scale from the Sun to Earth, the Moon orbits the Sun, just a litle more wobbly than the Earth’s path, by litle I mean well below the error when we imagine the Erath’s path as an elipse.
We can try to define if something goes around as orbiting, but If I pick two planet from our solar system one will goes around of the other, thechnically orbiting it? We can try to restricting the distance… but that is a problem as well, even worst idea that “nothing” comes in between: multiple moons? What about the moons’ moons?
Ahhh, humans and their need to neatly categorize things…
Help me understand the point you are trying to make. Are you trying to hand-waive categorization as superfluous to developing broader understanding?
Natural satellites fall within the primary body’s Hill sphere, where the gravity of the larger mass dominates. The Earth/Moon system co-orbits the sun. Saturn has two satellites that orbit each other, and that system co-orbits Saturn.
The point is on which influence yhe orjecy orbits another one. It’s clear that the orbiy arround Earth of the Moon is influenced also by the Sun and in less way even by the other planets, but itt orbits the Earth and not these “influencers”. Thedifference of orbit and gravitanional deviations is pretty clear.
Considering it’s in a double tidally locked orbit with its own moon Charon and the point that both rotate around is outside Pluto’s volume I would argue that the Pluto/Charon system is actually a dwarf-binary-planet.
At that point the only really ‘planety’ thing about is is basically that it is spherical.
Its not primarily orbiting the sun, so much as it is the barycenter of itself and charon.
And there are moons that are bigger, and more spherical, and more massive than Pluto.
And while it does have the vaguely heart shaped terrain feature, Mars has a smiley face crater, Saturn has an eternal hexagon on its north and south poles, despite being a gas giant, Jupiter has the spot, Mimas kinda looks like the Death Star, etc.
Also they shouldn’t have called the category of “things that aren’t planets despite being in some ways planet-like” “dwarf planet,” they should have called them “planetoids.” Star Trek had been referring to small planet-like objects as planetoids for decades, so the work in the popular consciousness had already been done. Dwarf planet not being a planet makes it sound like they’re saying dwarf people don’t count as people, and I don’t care for that at all.
You would think this is the case but they specifically decided through a vote that a dwarf planet is NOT a planet but a completely separate type of object. The whole vote was ridiculous and done at the very end of the conference so that only a fraction of the members were there to vote on pluto.
Edit: I’m down voted but every word of what I wrote is true. Dig into it and you will find out the same.
Then YOU come up with a definition of a planet that manages to include Pluto while simultaneously excluding Ceres, Charon, Eris, Cedna, Makemake, and 200+ other objects in the solar system large enough to be spherical, some of which are larger than Pluto
The definition of planet should be what it is, a traditional unscientific category based on history… like constellations.
Calling Mercury a planet and Jupiter a planet as though they are similar in almost any way is silly scientifically.
Perhaps leave the traditional planets category alone and create new categories that could pertain to all systems not just ours. Maybe something like terrestrial planets, gas planets, dwarf planets… etc. Categories that won’t have to change any time a new discovery is made.
And it has an orbit at a different angle than the 8 Planets and at it’s narrowest the ellipse of Plutos orbit is actually closer to the Sun than Uranus Neptune.
Edit: That moment when you‘re so done, you fuck up the order of our planets…
Size doesn’t matter
Size is a factor. But not everything.
Correct, it’s called planet when it orbits arround the Sun AND has cleaned it’s orbit from asteroids, not the case of Pluto, whose orbit is still full of other objects, some even bigger than Pluto itself.
If it orbits an Planet instead of the Sun, it’s a Moon, even if it is bigger than some other planets.
“All right, Ganymede. You can be a planet, but first you have to clean up your orbit. Start with Jupiter.”
Jupiter, largest of all dwarf planets, shares its orbit with some i don’t know million asteroids.
I’ve often thought that ‘clearing’ it’s orbit is misleading. I believe the definition ought to be changed to ‘controls’ or ‘governs’ its orbit. This allows for objects in stable L4/L5 locations without inviting the caveats that ‘clearing’ needs.
Its because its a colloquial phrase that more or less the media picked up and ran with.
Actual astronomers and astrophysicists use math to describe what they’re talking about, math that you can find and learn fairly easily on wikipedia.
Lay people tend to just evaluate a phrase for its extremely literal meaning, not realizing that it is at best just pop science jargon, short hand to refer to a pretty well defined and precise concept, that is difficult to summarize without losing specificity.
There are many, many other examples of this kind of thing happening with other phrases or terms used to refer to complex concepts.
If those asteroids are on the L1-5 points, they do not count. Since they will stay at that orbit forever.
(pragmatically speaking)
Jupiter has a permanent cloud of asteroids that follow it and neptune crosses the orbit of pluto so neither of those have cleared their orbits so of course they made exceptions so that their contrived definition fits.
Do you mean the asteroids at the Lagrangian points? Every single planet has asteroids there because math/physics dictates those points to be stable. Jupiter has the most at its points because it’s the largest planet.
Same with Neptune cleaning its orbit: It has collided with every single thing in its orbit EXCEPT those that synced their orbits to Neptune. An object that is gravitationally dominated by a single planet should not be a planet under any definition.
Sources because I had to read into your claims and I’m no astrophysicist:
https://en.wikipedia.org/wiki/Lagrange_point
https://en.wikipedia.org/wiki/Resonant_trans-Neptunian_object
Yes, that’s the made up exception. And for neptune not clearing its orbit due to pluto crossing that orbit? Well we have to make an exception for that so…um…the resonance between neptune and pluto. Exception achieved!
The rules are so contrived that it would not make sense for almost any other system except exactly ours. Whatever it takes to keep Earth’s category of “planet” important… you know… for reasons.
Very unscientific but very human.
No.
Lets try a more simple metaphor.
One person is navigating through a crowd, occasionally bumping into other people, having to juke and dodge their way around.
Another person has an entourage or body guards to their front, and two gaggles of papparazzi following behind them, at each 45 degree angle to their rear, as they walk through an entire empty street 4 lane street, with some occsional people walking past the whole scene on the sidewalk.
Pluto and Charon are basically an awkward, clumsy couple trying to get through a densely packed mall or convention.
Neptune is Taylor Swift, as an entire parade float, just, herself, body guards, papparazzi. And I guess she also can have some literal ingroup orbiters who manage to stick around, their lives revolve around her the same way their walking patterns do.
And then maybe, by chance, that awkward couple leaves the convention, gets lost, walks the wrong way to a restaurant, and end up just directly crossing the street that Swift walked down, 6 hours ago.
There, is that a sufficiently relatable visual metaphor to illustrate the difference between the two situations?
It’s a fine metaphor but it doesn’t work for scientific definitions which are exact. The IAU came up with the rule then had to make an exception to their own brand new rule in order to have Neptune remain a planet but not pluto even though both fail the rule. The exception is real and written down, not assumed.
Yet again another of the IAU rules is the body has to be assume hydrostatic equilibrium (nearly round). Mercury is NOT in hydrostatic equilibrium and they knew this. So they just…decided… that Mercury is a planet anyway and does not have to follow that rule.
So two planets don’t even follow the rules they made yet were unscientifically decided to be planets. Why? What was the point of it? Certainly wasn’t done for any scientific reason.
Ok, so, Pluto is more spherical than Mercury, but the most important criteria is local gravitational dominance.
Which Mercury has, but Pluto does not.
I do not see how this is a difficult concept to grasp.
Yeah, sometimes you can make a hasty definition, and then refine it to a level of consistent clarity, after it is justly critiqued, though that refined definition may be multi tiered and somewhat complex.
Thats… thats how science works, thats like the entire fundamental concept of it, right there, improving the level of detail to which you understand reality, via empiricism, logic, participatory debate.
The primary purpose of the planet defition refinenment is to emphasize the importance of relative local gravitational dominance.
I’m trying to imagine you using this kind of logic with like, biological taxonomy.
There is nothing difficult to grasp. They made rules then decided for no reason to let mercury break the rule. Why? Why not make mercury a dwarf planet instead of allowing it with no rule exception other than…just because.
This is not bioligical… those MUST follow the rules. This was a traditional unscientific list… Exactly like constellations. Why not start removing stars from constellations because they are too far away? Except a couple of them just because.
This IAU conference vote was not unanimous… it was very contentious and many wanted a more geological and broad definition rather than an earth centered definition that literally ONLY applies to our solar system. “Planets” can only exist around OUR Sun. Think about that.
Ah, yes. This is clearly justification for Pluto to become a planet! /s
If the only defense for your viewpoint is to throw out every definition and argument despite their validity, you aren’t arguing in good faith and have no facts to stand on
If the definition of a planet is that it has cleared is orbit then how is Neptune a planet? It shares its orbit with the dwarf planet pluto therefore they should both be dwarf planets correct?
You could just look up the actual astronomical or mathematical definitions of a ‘cleared orbit’ if you wanted to, you know that right?
https://en.wikipedia.org/wiki/Clearing_the_neighbourhood
Pluto and other plutinos are bodies whose orbits are significantly governed by Neptune.
Go look at all the numerical values provided by various algorithms that measure essentially the extent to which a celestial body is locally gravitationally dominant, the extent to which it has ‘cleared its orbit’.
You may notice that everything considered a dwarf planet scores orders of magnitude less, by literally all the metrics, than actual planets.
I understand the exception created for Neptune. But they had to create this exception… for their own brand new rule… in order to classify 8 things. Notice the exception is written very specifically just to keep pluto from “clearing” is orbit.
Another IAU rule is that the body must assume hydrostatic equilibrium(nearly round). Mercury does NOT assume hydrostatic equilibrium. They knew this.
Guess what? They just…decided…Mercury doesn’t have to follow that rule.
It was all done very unscientifically.
Edit: I want to add that now there are only 8 planets…in the universe. There are no other planets because the definition includes that they must “orbit the Sun”. Not a star but very specifically the Sun. All this with exceptions for just 8 objects? I’m telling you it was a power trip thing more than a scientific endeavor.
What rules do you believe make for a definition that isn’t contrived? How do you exclude asteroids from your definition or reject other dwarf planets like Ceres without making up contrived exceptions of your own?
Planets are round, naturally formed bodies orbiting a star. (I know no planet is perfectly round and you can call any defined tolerance “contrived”, but at that point there are no useful and universally fitting definitions for anything in nature. Definitions are always categorizations by human standards)
Many asteroids are round. The list of planets, under your definition, would be so large it isn’t useful anymore. Even when Ceres, Pluto, and Eris were called planets the list was getting too long, and there are several larger than Ceres. Including every nominally round object would be insane.
I propose a better definition:
Planets are very large objects orbitting a star that dwarf everything nearby
I’m pretty sure this is the intent of the IAU’s definition. It’s just more specific.
Ah, yes. “very large”, “dwarf everything”, and “nearby” are very specific terms…
Jupiter’s Trojan asteroids sit at Lagrange points. Material found there is not counted in the ‘clearing the orbit’ criteria. They are in stable orbits caused by the mass of the planet in question, not in lieu of a massive enough body.
Well of course that was the exception they had to come up with for their contrived rule. The exception is: “whatever it takes to make pluto not a planet”. Since the vote was agenda fueled and not a scientific discussion.
Once something new is discovered and breaks the rules they will have to modify the contrived rule to keep pluto not a planet.
And what agenda is that? To mine the planet in secret so not to upset the environmentalists?
Yes, that’s how science goes. Simple explanations and definitions often fall apart upon further discovery and require caveats that sometimes even reinforce the intention.
I agree except in this instance the goal was to keep Earth’s classification important. No other scientific objective. Just seemed very geocentric to me.
Hold on. What agenda wants Pluto to not be a planet?
“Something something something jews”
Someone printed out a buncha shirts with only 8 solar orbits in the system. Obviously easier to lobby Pluto off the team than to reprint the shirts.
Tbf, if you were going to keep Pluto in the definition you’d have to include 200+ other orbits
What is going to be funny is if/when they discover planet 9, and all the apparent Pluto superfans just utterly lose their shit when they attempt to comprehend that there can be another actual planet, and no, pluto still doesn’t count.
And they would have gotten away with it, if not for that one guy arguing about it on Lemmy in 2026.
However, if a moon is sufficiently large compared to its planet, it also gets to be a planet and part of a binary planet system, not a moon.
Aka the Charon-Pluto binary dwarf planet system
But how do we define what orbits what? On the scale from the Sun to Earth, the Moon orbits the Sun, just a litle more wobbly than the Earth’s path, by litle I mean well below the error when we imagine the Erath’s path as an elipse.
We can try to define if something goes around as orbiting, but If I pick two planet from our solar system one will goes around of the other, thechnically orbiting it? We can try to restricting the distance… but that is a problem as well, even worst idea that “nothing” comes in between: multiple moons? What about the moons’ moons?
Ahhh, humans and their need to neatly categorize things…
Just because 2 objects orbit around the same point doesn’t mean they orbit each other. Your entire argument is flawed.
We know what objects orbits each other because of the L4/L5 instability threshold.
Help me understand the point you are trying to make. Are you trying to hand-waive categorization as superfluous to developing broader understanding?
Natural satellites fall within the primary body’s Hill sphere, where the gravity of the larger mass dominates. The Earth/Moon system co-orbits the sun. Saturn has two satellites that orbit each other, and that system co-orbits Saturn.
The point is on which influence yhe orjecy orbits another one. It’s clear that the orbiy arround Earth of the Moon is influenced also by the Sun and in less way even by the other planets, but itt orbits the Earth and not these “influencers”. Thedifference of orbit and gravitanional deviations is pretty clear.
Pluto is a dwarf planet, which is still a planet.
Also, they absolutely should have just made an exception for Pluto so science teachers everywhere could have used that as a fun teaching point.
Considering it’s in a double tidally locked orbit with its own moon Charon and the point that both rotate around is outside Pluto’s volume I would argue that the Pluto/Charon system is actually a dwarf-binary-planet.
I’d okay with that. As long as it’s still technically a planet. (what? it’s my favorite!)
At that point the only really ‘planety’ thing about is is basically that it is spherical.
Its not primarily orbiting the sun, so much as it is the barycenter of itself and charon.
And there are moons that are bigger, and more spherical, and more massive than Pluto.
And while it does have the vaguely heart shaped terrain feature, Mars has a smiley face crater, Saturn has an eternal hexagon on its north and south poles, despite being a gas giant, Jupiter has the spot, Mimas kinda looks like the Death Star, etc.
Everyone loves an underdog
https://youtu.be/xgFKxFX3IwY I recommend watching this video
Also they shouldn’t have called the category of “things that aren’t planets despite being in some ways planet-like” “dwarf planet,” they should have called them “planetoids.” Star Trek had been referring to small planet-like objects as planetoids for decades, so the work in the popular consciousness had already been done. Dwarf planet not being a planet makes it sound like they’re saying dwarf people don’t count as people, and I don’t care for that at all.
Precedent for an exception would go to Ceres not Pluto.
The text book publishers are always looking for a reason to sell new editions.
https://science.nasa.gov/dwarf-planets/
https://astronomy.stackexchange.com/questions/18995/is-jupiter-a-dwarf-planet
You would think this is the case but they specifically decided through a vote that a dwarf planet is NOT a planet but a completely separate type of object. The whole vote was ridiculous and done at the very end of the conference so that only a fraction of the members were there to vote on pluto.
Edit: I’m down voted but every word of what I wrote is true. Dig into it and you will find out the same.
Then YOU come up with a definition of a planet that manages to include Pluto while simultaneously excluding Ceres, Charon, Eris, Cedna, Makemake, and 200+ other objects in the solar system large enough to be spherical, some of which are larger than Pluto
The definition of planet should be what it is, a traditional unscientific category based on history… like constellations. Calling Mercury a planet and Jupiter a planet as though they are similar in almost any way is silly scientifically.
Perhaps leave the traditional planets category alone and create new categories that could pertain to all systems not just ours. Maybe something like terrestrial planets, gas planets, dwarf planets… etc. Categories that won’t have to change any time a new discovery is made.
Unless you are Pluto.
Wasn’t it more bc it doesn’t clear it’s surroundings?
And it has an orbit at a different angle than the 8 Planets and at it’s narrowest the ellipse of Plutos orbit is actually closer to the Sun than
UranusNeptune.Edit: That moment when you‘re so done, you fuck up the order of our planets…
Do you mean Neptune? Pluto’s perihelion is 29.7 AU while Uranus’ aphelion is 20.1 AU.
Oh yea, sorry. I was tired, exhausted n stoned n fucked up the correct order of our planets
They did our boy dirty. Never forget!
That’s what I tell my wife but she won’t listen
Come on guys, laugh
We’re laughing with your wife.
What have I done
Oh honey it’s ok
That’s not what she said.