If you turn on the 'Stars' in that, you'll see that its currently in the interesting direction of the sky - 'twards the center of the Milky Way where we've got other telescopes looking. I wonder if we would have detected it if it was 180° further in its orbit.
There was a lot of negative press and commentary about "demoting" Pluto from being a planet at the time. But its obviously true that it was the right move, and creating this "dwarf planet" class of objects was correct. It was hard to justify Pluto being a planet when Ceres exists, but Eris, Haumea, Makemake and all of these other possible Dwarf planets are the nail in the coffin.
Nah, what we need to do is to just extend our heads to be 2 categories and not think of one as lesser or demotion.
Like, in high fantasy, right, we have humans and elves and dwarves and orcs and all that. Are dwarves 'less' than elves? Are orcs 'less' than humans? No, they exist on a spectrum or line that is not less or more. Maybe less or more evil, maybe less or more aged or fancy. But in high fantasy you can't demote a elf to be a dwarf or a human into an orc. |
So, my proposal: Include all the dwarf planets in all the science exhibits, the kindergarten posters, the rhymes and meters. Just like with the upper and lower cases of the Latin alphabet. Sure you can forget that the dwarf ones exist, but if it's on everything, then that'll be hard.
Here's a quick one that I put like no thought into:
>Mercury, Venus, here comes Earth!
>Mars is next, let's shout with mirth!
>Jupiter's big, Saturn has rings,
>Uranus and Neptune make eight amazing things!
>Ceres, Pluto, Haumea too!
>Makemake and Eris join the crew!
>Sedna, Quaoar, Orcus, Gonggong,
>Dwarf planet dancing all day long!
So, again, sure, dwarves, fine. But just don't make being a dwarf planet a 'thing', celebrate them too!
> But its obviously true that it was the right move, and creating this "dwarf planet" class of objects was correct. It was hard to justify Pluto being a planet when Ceres exists, but Eris, Haumea, Makemake and all of these other possible Dwarf planets are the nail in the coffin.
I don't agree that "its obviously true that it was the right move". Instead of demoting Pluto, they could have promoted Ceres, and let Eris, Haumea, Makemake, etc, be planets too. Under that proposal, they could even have the category of "dwarf planets" encompassing them, it is just that "dwarf planet" would be a subcategory of planets rather than a disjoint category from them.
Classifications are useful. Even the 'proper' planets we split into terrestrials, Jovian giants, and ice giants. Each planet is individually interesting in itself. One might even argue all of the bodies in the Solar System exist on a continuum of mass from the tiniest mote of space dust, to rocks and asteroids, to moons and dwarf planets to terrestrial planets, ice giants, giants, and then the Sun, and then hypergiant stars, neutron stars, black holes, and then supermassive black holes, so let's call all of them 'celestial objects'—which we kind of do. But such a catch-all is pointless. Each object behaves very differently, with wildly different physical laws governing its interior and its neighbourhood.
Classifications impose structure on a collection of celestial objects, and we can derive relationships, commonalities, understand their development, the physics governing these objects, and build useful physical and mathematical models to widen our understanding of the universe.
Most reasonable scientists understand that some of these objects will blur the edges—like many moons being more massive and larger than Mercury. Or like the largest super-Earth exoplanets being nearly as massive as Neptune, or the largest gas giant exoplanets being 30-80 times as massive as Jupiter and hence having a surface temperature of ~2000 K. But that is part of science, and possibly even where the most interesting work is.
Classifications are useful! It is poor form to take a widely used and historic term and add on a whole different (dynamic!!) category of attribute as a filter on the definition. There is quite a bit of absurdity in the 2006 IAU's definition of a planet. If a massive object came into the solar system and perturbed orbits, caused chaos and collisions, then any "planet" with debris within its neighborhood would cease to be a planet. What do we gain from adding a whole different category of attribute (relationship to its neighborhood) as a criterion? Does it realistically outweigh decades or centuries of peoples intuition of the existing definition? Its not just a matter of science, but language and communication. If you want greater specificity, come up with a new term or use compounded terms.
It very much seems like the definition was just shoe-horned to stem any more planets needing to be added. It would be interesting to know if astronomers walk the walk when it comes the definition. If I research when planets were formed would I get the date when their neighborhoods were cleared? Do discussions around large events that send debris into the neighborhood of planets correctly reflect that they cease to be planets until it is cleared?
Alan Stern said it best
>"We're going to call it a cow, except when it's in a herd." A river is a river, independent of whether there are other rivers nearby. In science, we call things what they are based on their attributes, not what they're next to.
>And the IAU definition is even worse, because it produces different categorizations for identical objects, depending on where they are. Get this — Earth at the same distance from the sun [as Pluto] would not be a planet by the IAU’s measure, because Earth can’t clear that zone either. I would say any definition that produces a result where Earth is not a planet under any circumstance is immediately indicted as ridiculous, because one thing we all agree is a planet is planet Earth!
>That's crazy. No wonder teachers and students are frustrated, confused, unhappy. It reflects poorly on astronomy, to have something so illogical.
I find this interview very interesting, because around a decade prior, Stern himself proposed 'clear the neighbourhood'[1] as a finer-grained rule for planet classification involving the dynamics of the planetary body in question. That is, planets that could clear their neighbourhoods are überplanets; otherwise unterplanets. In fact, near the end of that paper he proposes not two, but five classifications of planets: subdwarf, dwarf, subgiant, giant, and supergiant.
Now, Stern's broader argument in that interview is that we should not take into account the dynamical behaviour of planets. I disagree, especially since dynamics determine the static future state of any given object. Take chthonian planets—former gas giants whose gaseous envelopes have been stripped away by the primary. Do we insist that they are still gas giants? No, we even came up with a name for the transitory period when these planets are losing their gas envelopes.
Personally, I think Stern was being a little more animated to drum up support for and shine a beacon on New Horizons, a then-ongoing mission that he was principal investigator of.
To directly answer your question:
> If a massive object came into the solar system and perturbed orbits, caused chaos and collisions, then any "planet" with debris within its neighborhood would cease to be a planet.
There actually are (multiple) mathematical formulations for 'clearing the neighbourhood'[2]; Stern himself proposed one in the above-mentioned paper. Jean-Luc Margot suggests several more[3].
> Does it realistically outweigh decades or centuries of peoples intuition of the existing definition?
People's intuition for 'planet' in the centuries before telescopes were invented was 'something that moves against the fixed background of stars'—that is literally the Greek etymon for the English 'planet'. The Sun and Moon used to be a part of the 'classical planets'. We didn't even find the last two (or three) planets in our own Solar System until around two centuries ago.
We have repeatedly and retroactively renamed, retconned, reworked, revamped and rewound scientific definitions over and over again. I think planets will be OK.
I find it particularly amusing that the IAU definition, in a footnote, expressly declares the eight planets to be what they are. In other words, the true definition for being a planet is to be defined as a planet- so the criteria it gives are entirely superfluous, at least when it comes to our own solar system.
It's clear that they worked backwards from the eight planets to come up with a classification system that fit, but in realizing the problems with the approach, just gave up and created the carve-out.
Also, just as another example of the absurdity of the IAU definition, there's a pretty strong argument to be made that Earth's moon would be a planet under the criteria: it orbits the sun, it's round, and it's massive enough / positioned such that it's capable of clearing its neighborhood.
Yes, regardless of the specific labels, there are clearly interesting and meaningful differences between these things, and it’s worth having vocabulary capable of distinguishing them. The whole universe is a continuum of stuff but it helps to have more than just the word “stuff”.
Arguably there are just two categories: stuff and not-stuff (aka vacuum). And then you go from intergalactic space (almost entirely not-stuff) via interstellar space (marginally more stuff) through planets and stars up to neutron stars (lots of stuff) to black holes (well, we don't actually know what is inside a black hole exactly, our models break down).
Is this classification useful for everyday life? Not at all, but looking at things from different perspectives for a change can be quite amusing.
Yeah. The gas giants are clearly way different from rocky planets and we still keep them all under one taxonomical grouping. Pluto and other bodies should have been an extension of that: make them dwarf planets or whatever other classification you want. But they're still planets. Theres no "demotion" just a further categorization.
Right. Somewhat similar to other dual-use words like “work”, “energy”, “power”, “momentum”.
With such “well, ackshually”s as “you didn’t really do any work at all when you were pushing on that tree trunk” and “you specified watts, but you really wanted to use lumens”.
Yeah, I don't like when a modifier is mandatory. If they chose to label them "dwarf planets" then it should be expected that people will leave off the modifier "dwarf" when being concise.
If they really didn't want people to continue to refer to them as planets, then they should have chosen a completely different noun.
Yes. I wouldn't call a dwarf person any less of a person, nor would i refer to a dwarf planet as being any less a planet. Between the terrestrial planets, the gas giants, the ice giants, and arguably a couple of rounder moons, we have far more than 50 planets in our solar system.
By some extreme definitions, Earth might not be a planet. Some say the moon is too big to qualify the earth "cleared out its orbit" criteria, making Earth-moon some sort of double planet... like Pluto-Charon.
Setting aside the whole "demote Pluto" and "dwarf planet" aspects, I find it amusing that we use the same term for small rocky Mercury (2,440 km radius, 5% of Earth's mass) and immense gaseous Jupiter (69,000 km radius, over 300 times Earth's mass). Only we don't, of course. Jupiter is a gas giant, while Mercury is a rocky planet, or iron planet; there's a lot of 'planet' terminology.
Ultimately these sorts of quibbles are fundamentally semantic in nature thus (in general) entirely pointless. It's only the subjects themselves - the myriad celestial bodies - that are interesting.
It's semantics as well as a collision with our inability to work with gradients. We can look at two colours and can name the discrete ones - but when does red stop being red? When does a species emerge?
Why is Jupiter in the same category as planets then?
Jupiter does not orbit the sun (the first requirement per IAU definition of planet), the barycenter for the system is not inside the surface of Sol at 1.07 solar radius.
It is not planet then yes ? There is no push to promote it to a sub-brown dwarf or a new category .
Classifications are always arbitrary and only fits some bias one way or other.
a) orbits a star, and is not a star nor a brown dwarf itself;
i) a star is an object that is massive enough and hot enough to conduct protium fusion in its core
ii) a brown dwarf is an object that is massive enough to conduct deuterium fusion, but insufficiently massive (and hence insufficiently hot) for protium fusion
b) has attained hydrostatic equilibrium, that is, it is spheroidal;
c) it has cleared its local neighbourhood of 'rival planets' since its birth;
Ergo, Jupiter is a planet. It is a certain type of planet—a gas giant—but a planet nonetheless.
There is some controversy about when giant planets stop being giant planets and start being brown dwarfs—typically around 30 Jupiter masses—but this is an active area of research, to understand the fusion ignition in these objects. As I mentioned in another comment, classifications are useful. Of course they are arbitrary and they are biased—they were decided by humans. But the entire point of science is to push the edges of our understanding and reduce these biases and make our models more general and less arbitrary.
Everything orbits a barycentre. The position of that barycentre within or without the primary is not really relevant within several orders of approximation—and when it does become relevant, then that system becomes interesting in itself. Chances are the planet in question is so massive relative to its primary that we need to ask a more fundamental question: are we even looking at a star-planet relationship, or is it closer to a binary star system? Then we can investigate how that system formed and developed, and generalise and improve our model of stellar/planetary system development.
There are plenty of binary star systems where this orders of magnitude standard is not met .
There is no academic literature or accepted consensus barycenter has to be orders of magnitude away - the accepted consensus is that a body orbiting another means internal barycenter, if they have external barycenter then they orbit each other period.
The fact that Charon and Pluto do not have internal barycenter is why Pluto-Charon (also Eris-Dysonmia) are considered dwarf planet systems ; and that was used partly in support (while not used in definition) of arguing for dwarf status of Pluto .
Yes — their point is that as-written, it orbits a barycenter external to the star: hence doesn’t orbit the star, but they’re in a mutual orbit.
Thus the suggestion for a new dwarf category — precisely because we do label times the barycenter is outside the star differently, as you yourself note.
You were so busy trying to “correct” me, you failed to address the topic.
I agree with this picture as the barycenter argument seals it for me. The only leap left is for me to believe Ol'Jove as a failed star (it still emits heat in excess of what it derives from Sol) and we find ourselves cozily herded about by a binary star system.
I initially assumed from your comment that all of those objects are larger than Pluto, but none of them are, so what exactly is "obvious" about the decision? They haven't resolved any inconsistency by demoting it.
You merely need to define the term "NinePizza", which is a collection of nine pizzas—and then have your very educated mother serve that. This doesn't present any problems philosophically, since we already have terms like "Solar System" for collections of disconnected objects.
Does Saturn have enough density to count, though? I mean, from a certain point of view, it's more of a spheroid of hydrogen with a bit of helium. Maybe we need a new term for it, like "Planetary nebula"? ;)
Ceres by itself doesn't really challenge Pluto's old classification. Pluto has 14 times the mass of Ceres, and five moons. Ceres is the only "dwarf planet" classified so far that has zero moons. There are still good arguments for a definition that doesn't consider Ceres a dwarf planet.
This helps illustrate how arbitrary these classifications are. They depend entirely on what properties are included in the definition. The updated IAU definition is essentially reverse engineered to fit how they wanted to classify the planets.
So, a factor of 14.4 is enough to put the line between Ceres and Pluto, but a factor of 23.0 is not enough to put it between Pluto and Mercury?
Yes, those classifications are arbitrary, but then any classification is. If you want to consider Pluto as a planet, you have to include quite a lot of other bodies, which are all qualitatively and quantitatively different from the 8 (which themselves are in 2 qualitatively and quantitatively different groups. Or 3, depending on who you ask).
In the grand scheme of things, it does not matter and astronomers won’t care about the general public’s feelings. It is utterly pointless to get worked up about these things.
The problem is not experts having precise terminology in technical settings; the problem is the army of “experts” who will descend upon you if you use the incorrect arbitrary term in colloquial settings. The same sort that will descend on you if you dare refer to a planet orbiting a different star as a planet, not an exo-planet.
> The updated IAU definition is essentially reverse engineered to fit how they wanted to classify the planets.
I wholeheartedly agree with this take. I have something of a personal hatred of poorly executed retconning thus I present the following proposal.
For the sake of simplicity we should use even powers of 10 with earth as the primary reference point. Note that the earth is 10^24, mars is 10^23, and the earth's moon is 10^22 (pluto is also 10^22 and less massive than the earth's moon). It seems "obvious" then that 23-25 are planets, 22 or less are relegated to dwarfs, and 26 and over are giants (jupiter is a 27 and the sun a 30 for reference).
By that logic, if we want to consider pluto a planet then the earth's moon also has to qualify. I don't really care one way or the other but that just doesn't seem sensible to me.
> The new dwarf planet candidate, called 2026 ED138, orbits on a plane tiled nearly 25 degrees
I've noticed similar glaring typos in 2 recent articles. In both cases very early in the article. Is it possible that they are adding typos intentionally to mask the AI authoring?
(This uses wasm, meant for a desktop, and will download the asteroid catalog of about 65mb, you have been warned)
https://dahlend.github.io/ketev/#t=2009-07-01.717&sel=2026%2...
This is a big boy.
but it's not great for mobile
Like, in high fantasy, right, we have humans and elves and dwarves and orcs and all that. Are dwarves 'less' than elves? Are orcs 'less' than humans? No, they exist on a spectrum or line that is not less or more. Maybe less or more evil, maybe less or more aged or fancy. But in high fantasy you can't demote a elf to be a dwarf or a human into an orc. |
So, my proposal: Include all the dwarf planets in all the science exhibits, the kindergarten posters, the rhymes and meters. Just like with the upper and lower cases of the Latin alphabet. Sure you can forget that the dwarf ones exist, but if it's on everything, then that'll be hard.
Here's a quick one that I put like no thought into:
>Mercury, Venus, here comes Earth!
>Mars is next, let's shout with mirth!
>Jupiter's big, Saturn has rings,
>Uranus and Neptune make eight amazing things!
>Ceres, Pluto, Haumea too!
>Makemake and Eris join the crew!
>Sedna, Quaoar, Orcus, Gonggong,
>Dwarf planet dancing all day long!
So, again, sure, dwarves, fine. But just don't make being a dwarf planet a 'thing', celebrate them too!
I don't agree that "its obviously true that it was the right move". Instead of demoting Pluto, they could have promoted Ceres, and let Eris, Haumea, Makemake, etc, be planets too. Under that proposal, they could even have the category of "dwarf planets" encompassing them, it is just that "dwarf planet" would be a subcategory of planets rather than a disjoint category from them.
Classifications impose structure on a collection of celestial objects, and we can derive relationships, commonalities, understand their development, the physics governing these objects, and build useful physical and mathematical models to widen our understanding of the universe.
Most reasonable scientists understand that some of these objects will blur the edges—like many moons being more massive and larger than Mercury. Or like the largest super-Earth exoplanets being nearly as massive as Neptune, or the largest gas giant exoplanets being 30-80 times as massive as Jupiter and hence having a surface temperature of ~2000 K. But that is part of science, and possibly even where the most interesting work is.
It very much seems like the definition was just shoe-horned to stem any more planets needing to be added. It would be interesting to know if astronomers walk the walk when it comes the definition. If I research when planets were formed would I get the date when their neighborhoods were cleared? Do discussions around large events that send debris into the neighborhood of planets correctly reflect that they cease to be planets until it is cleared?
Alan Stern said it best
>"We're going to call it a cow, except when it's in a herd." A river is a river, independent of whether there are other rivers nearby. In science, we call things what they are based on their attributes, not what they're next to.
>And the IAU definition is even worse, because it produces different categorizations for identical objects, depending on where they are. Get this — Earth at the same distance from the sun [as Pluto] would not be a planet by the IAU’s measure, because Earth can’t clear that zone either. I would say any definition that produces a result where Earth is not a planet under any circumstance is immediately indicted as ridiculous, because one thing we all agree is a planet is planet Earth!
>That's crazy. No wonder teachers and students are frustrated, confused, unhappy. It reflects poorly on astronomy, to have something so illogical.
https://www.space.com/12710-pluto-defender-alan-stern-dwarf-...
Now, Stern's broader argument in that interview is that we should not take into account the dynamical behaviour of planets. I disagree, especially since dynamics determine the static future state of any given object. Take chthonian planets—former gas giants whose gaseous envelopes have been stripped away by the primary. Do we insist that they are still gas giants? No, we even came up with a name for the transitory period when these planets are losing their gas envelopes.
Personally, I think Stern was being a little more animated to drum up support for and shine a beacon on New Horizons, a then-ongoing mission that he was principal investigator of.
To directly answer your question:
> If a massive object came into the solar system and perturbed orbits, caused chaos and collisions, then any "planet" with debris within its neighborhood would cease to be a planet.
There actually are (multiple) mathematical formulations for 'clearing the neighbourhood'[2]; Stern himself proposed one in the above-mentioned paper. Jean-Luc Margot suggests several more[3].
> Does it realistically outweigh decades or centuries of peoples intuition of the existing definition?
People's intuition for 'planet' in the centuries before telescopes were invented was 'something that moves against the fixed background of stars'—that is literally the Greek etymon for the English 'planet'. The Sun and Moon used to be a part of the 'classical planets'. We didn't even find the last two (or three) planets in our own Solar System until around two centuries ago.
We have repeatedly and retroactively renamed, retconned, reworked, revamped and rewound scientific definitions over and over again. I think planets will be OK.
[1]: https://doi.org/10.1017/S1539299600013289
[2]: https://en.wikipedia.org/wiki/Clearing_the_neighbourhood
[3]: https://doi.org/10.1088/0004-6256/150/6/185
It's clear that they worked backwards from the eight planets to come up with a classification system that fit, but in realizing the problems with the approach, just gave up and created the carve-out.
Also, just as another example of the absurdity of the IAU definition, there's a pretty strong argument to be made that Earth's moon would be a planet under the criteria: it orbits the sun, it's round, and it's massive enough / positioned such that it's capable of clearing its neighborhood.
Is this classification useful for everyday life? Not at all, but looking at things from different perspectives for a change can be quite amusing.
I find people do this a lot with space stuff because they're interested in it but don't really know much about it.
It's ultimately irrelevant to the subject at hand and detracts from the conversation.
https://en.wikipedia.org/wiki/Law_of_triviality
https://en.wikipedia.org/wiki/Lumpers_and_splitters
Just expect to be corrected and "well, achually"-ed by people who follow the current naming system, especially in science circles.
With such “well, ackshually”s as “you didn’t really do any work at all when you were pushing on that tree trunk” and “you specified watts, but you really wanted to use lumens”.
If they really didn't want people to continue to refer to them as planets, then they should have chosen a completely different noun.
My Very Elegant Mother Just Served Us Nachos
By some extreme definitions, Earth might not be a planet. Some say the moon is too big to qualify the earth "cleared out its orbit" criteria, making Earth-moon some sort of double planet... like Pluto-Charon.
https://en.wikipedia.org/wiki/List_of_planet_types
Jupiter does not orbit the sun (the first requirement per IAU definition of planet), the barycenter for the system is not inside the surface of Sol at 1.07 solar radius.
It is not planet then yes ? There is no push to promote it to a sub-brown dwarf or a new category .
Classifications are always arbitrary and only fits some bias one way or other.
There is some controversy about when giant planets stop being giant planets and start being brown dwarfs—typically around 30 Jupiter masses—but this is an active area of research, to understand the fusion ignition in these objects. As I mentioned in another comment, classifications are useful. Of course they are arbitrary and they are biased—they were decided by humans. But the entire point of science is to push the edges of our understanding and reduce these biases and make our models more general and less arbitrary.
There is no academic literature or accepted consensus barycenter has to be orders of magnitude away - the accepted consensus is that a body orbiting another means internal barycenter, if they have external barycenter then they orbit each other period.
The fact that Charon and Pluto do not have internal barycenter is why Pluto-Charon (also Eris-Dysonmia) are considered dwarf planet systems ; and that was used partly in support (while not used in definition) of arguing for dwarf status of Pluto .
Thus the suggestion for a new dwarf category — precisely because we do label times the barycenter is outside the star differently, as you yourself note.
You were so busy trying to “correct” me, you failed to address the topic.
This helps illustrate how arbitrary these classifications are. They depend entirely on what properties are included in the definition. The updated IAU definition is essentially reverse engineered to fit how they wanted to classify the planets.
Yes, those classifications are arbitrary, but then any classification is. If you want to consider Pluto as a planet, you have to include quite a lot of other bodies, which are all qualitatively and quantitatively different from the 8 (which themselves are in 2 qualitatively and quantitatively different groups. Or 3, depending on who you ask).
In the grand scheme of things, it does not matter and astronomers won’t care about the general public’s feelings. It is utterly pointless to get worked up about these things.
I wholeheartedly agree with this take. I have something of a personal hatred of poorly executed retconning thus I present the following proposal.
For the sake of simplicity we should use even powers of 10 with earth as the primary reference point. Note that the earth is 10^24, mars is 10^23, and the earth's moon is 10^22 (pluto is also 10^22 and less massive than the earth's moon). It seems "obvious" then that 23-25 are planets, 22 or less are relegated to dwarfs, and 26 and over are giants (jupiter is a 27 and the sun a 30 for reference).
By that logic, if we want to consider pluto a planet then the earth's moon also has to qualify. I don't really care one way or the other but that just doesn't seem sensible to me.
Pretty rad.
https://en.wikipedia.org/wiki/Planets_beyond_Neptune
I've noticed similar glaring typos in 2 recent articles. In both cases very early in the article. Is it possible that they are adding typos intentionally to mask the AI authoring?
(Character limit 280)