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Since it was stripped of planetary status, Pluto’s defenders have been fighting

52 pointsby ziofillyesterday at 6:05 AM176 commentsview on HN

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adrian_byesterday at 7:07 PM

> “One of the biggest flaws with the IAU definition is that you can have the same object in two different orbits,” says Kornfeld. “In one, it’s considered a planet, and in the other, it’s not considered a planet.”

No, there is no flaw in this, and moreover there is nothing new in this. This is how it has always been, it is not something invented recently.

In the Solar System, there are 3 Mercury-sized satellites and other 3 Moon-sized satellites, besides the Moon. If they had not been in their orbits as satellites, they might have very well been planets. Therefore the old definition of "planet" also depended on the orbit of the body, not only on the size and shape of the body.

Most of those satellites are bigger than Pluto. Triton, the biggest satellite of Neptune, had been in the distant past another planet with an orbit close to Pluto, but it was captured by Neptune and it has become a satellite. Otherwise it would have remained a "dwarf planet", orbiting close to Pluto. So Triton was demoted from "planet" to "satellite", by Nature, not by a human organization.

The current definition of "planets" and "dwarf planets" is fine.

If anything, there are too few planet classes, not too many. A more useful classification is into big planets, medium planets and small or dwarf planets, where the Solar system has 4 big planets, 4 medium planets, and a lot of small planets.

The big planets, i.e. which are big enough to retain the volatile chemical elements, like hydrogen and noble gases, not only the refractory elements, have a very different chemical composition from the medium planets, and this difference will also exist in any other stellar system that has condensed from gases like those at the origin of the Solar System, with more oxygen than carbon (there exists the possibility of stellar systems with a different chemical composition than the Solar System, formed by condensing from gas mixtures with more carbon than oxygen).

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paxystoday at 1:03 AM

The "battle" for Pluto is an interesting case study in indoctrination. A few generations of children grew up being taught a specific fact, saw it in textbooks, learned mnemonics about it, had memorable cartoon characters named after it, and then one day they were told – with sound reasoning and plenty of scientific evidence – that they should now update their views on the topic.

You would think this group of well educated, critically thinking adults would go "sure", but something fundamental in their brains just refuses to let them accept this meaningless change to their lives.

Now scale this up to actual impactful topics like religion, politics, relationships, race and more and most conflicts around the world start to make sense.

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llodayesterday at 8:33 PM

Pluto was only discovered in the 1930s. The only cultural heritage of Pluto as a ‘planet’ is a few decades of science schoolbooks, but going by these comments you'd think it's been in the same list as Jupiter since the Babylonians.

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Planktonneyesterday at 7:19 PM

The actual problem here is weirdly aggressive nerds who are incapable of nuance, and insist that an astronomical classification (Pluto is not a planet by the IAU definition) should be used in non-astronomical contexts.

Historically and culturally, Pluto is considered a planet. An IAU classification shouldn't be used to try and retroactively change that, because the IAU does not have control over history and culture. It's a fun fact (did you know that Pluto is not classified as a planet by astronomers?) not a diktat.

Similarly, a banana is 'officially' a berry, which means that it is classified as a berry by botanists. This does not mean it is considered a berry in any other contexts. If you told someone you had made a berry crumble and it was filled with bananas, you would look strange. We have countless examples of this (often focused around food): a tomato does not belong in a fruit salad no matter what botanists say.

Different terms are used with different specificity in different settings. Language and culture and [older disciplines] are not governed by the rules of [newer disciplines or bodies]. If people with 'I love space' t-shirts would stop "um actually"-ing, no one would have a problem.

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drxzclyesterday at 6:55 PM

> “One of the biggest flaws with the IAU definition is that you can have the same object in two different orbits,” says Kornfeld. “In one, it’s considered a planet, and in the other, it’s not considered a planet.”

So… planet Ganymede when? Or Titan?

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odyssey7yesterday at 7:30 PM

The problem is that the word “planet” refers both to cultural symbols — mythology, gods, archetypes, and the heavens — and to objects of scientific study. Those are different domains, and one of them is cultural heritage, and the other is irritating when it tries to infringe on the first one.

There’s no need for a god complex. Stop picking and choosing which planets are real. Scientists can create their own, more precise words for things. Planets are sacred. Things that clear their orbits are not.

You can’t subdue the public into giving up their gods out of difference to science — you’re just losing people.

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pfdietzyesterday at 10:38 PM

The obvious solution to this issue is to destroy Pluto.(*)

Many problems can be solved by application of sufficiently powerful explosives.

(*) Or, possibly, eject it from the Solar System.

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bryanlarsenyesterday at 7:14 PM

The main objection to calling Pluto a planet appears to be that if Pluto is a planet then up to about 200 other objects should also be called planets, that the list would be of unknown size and regularly changing.

That's an objection? No, that's a benefit! I think it'd be awesome to be regularly discovering new planets.

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jerfyesterday at 7:08 PM

You know, this is really just a fantastic opportunity to realize the phenomenal psychological power of "headcanon". Who cares if Pluto is or is not tagged with the word "planet" by some organization you know effectively nothing about, have no control over, has no control over you, and couldn't so much as move a pebble on the planetary body in question any time in the next 20 years, if not more?

Have whatever emotional relationship you like with "Pluto" and don't wait around for others to validate it. It's fine. Nobody can stop you. I'm a bit fond of Ceres myself. Nobody can stop me. Nobody needs to approve it. Take control. Write your own headcanon.

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jsbisviewtifulyesterday at 7:10 PM

In case anyone was curious, the Moon is bigger than Pluto. Pluto's 2/3 the size of the Moon. If any dwarf planet should be upgraded to a planet, it's Eris. Eris's diameter is over 600km bigger than Pluto's.

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5555624yesterday at 9:11 PM

As fare as I'm concerned, Pluto is a planet. I've got a hand-written note from Clyde Tombaugh that says so. Back in the mid-1990s, a year or two before he died, I write him asking about some astronomers who were starting to question it.

hn_submityesterday at 6:58 PM

I'm in the same camp. I believe the classification of Pluto as a dwarf planet was arbitrary and inconsistent. I mean, it's been known as a planet for almost 80 years and suddenly we demote it?

I believe someone was trying to make a name for themselves here and ignoring the history of Pluto and its discovery.

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Syzygiestoday at 12:10 AM

My favorite nonfiction book in years is "Storia della pasta in dieci piatti" by Luca Cesari. The signature chapter explores the day in 2015 when celebrity chef Carlo Cracco stated on television that a clove of garlic is an ingredient that can go into amatriciana. Cesari explores the absurdity of the resulting uproar, given the actual history of the dish.

People like to make rules. Leave them be in their tree houses, unless you really like to play too. I thought it was a right of passage in high school to laugh at the French forming committees to tell peasants how to speak their native language. We haven't generalized from this example?

Who gives a rat's ass whether this governing body thinks Pluto is a planet or not?

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Sharlinyesterday at 7:15 PM

This seems like the least important issue in the world to keep complaining about.

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Shuddownyesterday at 10:23 PM

Could someone explain what the IAU means by "clearing its orbit". For example, could we consider the Earth having not "cleared its orbit" because of the Moon? The Sun attracts the Moon more strongly that Earth does, so does that mean that the Earth doesn't fit the criteria? Or does the IAU have some sort exception for moons which they've defined some place else? I'd really appreciate if someone with more knowledge could explain.

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ecliptikyesterday at 7:30 PM

It's dumb, but whenever I see something representing the planets, I always count them. Occasionally you come across places that still include Pluto.

Most recent example I found was the Swatch MoonSwatch Collection [1], which includes the Sun, Moon, eight planets and Pluto[2].

1. https://www.swatch.com/en-us/bioceramic-moonswatch-collectio...

2. https://www.swatch.com/en-us/mission-to-pluto-so33m101/SO33M...

tehologistyesterday at 11:51 PM

OMG, I was taught there was 9 planets my whole life. I had no idea there is now 8 planets in the solar system. My very educated mother just sold nine....

sebbultoday at 12:36 AM

Classification is a human invention… are tomatoes, cucumbers and zucchinis fruit or veggies? Non issue.

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wpollocktoday at 1:23 AM

[Edited for clarity.] My issue with the IAU's definition is that the body must "orbit the Sun". I would prefer they said "star" instead, and excluded other stars (so a binary star means neither star is a planet).

mhabetoday at 1:24 AM

If the IAU had any sense they would have made Ceres a planet instead of axing Pluto. These decisions should be made in a way that makes funding exploratory missions as easy to sell as possible. Pluto the planet wis easier to sneak through congressional budgets than Pluto the Dwarf planet. Instead of waxing poetic on the Platonic form of planet, just draw a wide line around things people want to get probes sent too without going so broad as to lose the plot. Even better would have been to give Pluto a designation like the nearest Rim Planet, implying there are so many strange Rim Worlds for us to find and explore.

KineticLensmanyesterday at 6:46 PM

"How I Killed Pluto and Why It Had It Coming" - awesome title for an Astronomy book

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tehnoslowyesterday at 7:27 PM

The claim that the IAU vote was procedurally invalid is interesting

kazinatoryesterday at 7:21 PM

> Pluto represents the underdog ...

I see what Schindler did there!

Oarchyesterday at 7:01 PM

Back in school I learned the acronym:

My Very Easy Method Just Speeds Up Naming Planets

And it was so convenient! Does anyone know a good alternate now that the P is gone?

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atmavataryesterday at 9:30 PM

Back in my day, we had nine planets.

GrumpySciGuyyesterday at 7:24 PM

Let the experts decide same with any other field.

jscdyesterday at 10:30 PM

I truly don't get why people have so much reverence for Pluto. And, unlike something like "fruit," which has a botanical and culinary definition which serve different purposes, I really don't get why anyone would care about the non-scientific definition of planet. Maybe I'm just ignorant here: what's the cultural significance of some celestial object being considered a planet?

baggy_troughyesterday at 7:27 PM

The correct planet criteria are, IMHO:

- not a star

- not orbiting a planet

- roundish

- greater than 1000km radius

That would restore Pluto to its rightful place and add Eris.

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animitronixyesterday at 7:25 PM

It's time to give it up. Nobody wants there to be 23 planets...

adolphyesterday at 6:57 PM

It seems as though Pluto's primary problem is "clearing the neighbourhood." Given Pluto's orbit travels closer and further from the sun than Neptune, does Neptune also have the neighborhood clearing problem since it has not cleared Pluto?

  In celestial mechanics, "clearing the neighbourhood" (or dynamical dominance) 
  around a celestial body's orbit describes the body becoming gravitationally 
  dominant such that there are no other bodies of comparable size other than 
  its natural satellites or those otherwise under its gravitational influence.[0]
  
https://en.wikipedia.org/wiki/Clearing_the_neighbourhood
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baggy_troughyesterday at 6:48 PM

Bring back Pluto!

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d--byesterday at 10:13 PM

Humanity's need to categorize things never ceases to amaze me.

Is it Art? It's not Art! Are bananas a vegetable or a fruit? Pluto definitely is a planet! No it's not!

Jesus, what a waste of energy.

Are we just realizing that asteroids come in all sizes? Do we really need a sharp boundary between those we call planets and those we don't call planets?

Can we consider planethood a spectrum? Like should we REALLY care if someone says there are 9 planets in the solar system, and the next person says 8?

We used to say there were 3 oceans, now there are 5. In reality, there's just one big saltwater lake. Do people fight about where one ocean ends and where the next one starts?

Let them call pluto a planet if they want, let them call pluto a kuiper object.

We shouldn't give a fuck.

metalmanyesterday at 7:28 PM

Pluto as one of the outer Canadian planets in the Canadian solar system, which as you now know is part of the Canadian Galaxy is realy such a trifling concern back on one of the Canadian Continents that contains Canada proper the center of Universal Canada, but since there is dissent on it's status something can be done through a referendum. go ahead,laugh, but wait till google AND wikipedia both come on board

heyitsmedotjaybyesterday at 6:50 PM

It's been renamed to Planet America, thank you for your attention on this matter.

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davidguettayesterday at 9:17 PM

Pluto is a planet.