How did Pluto get demoted? What makes a planet a planet anyway? Why do we now have so many different kinds of planets, and should we make things simpler? I discuss these questions and more in today’s Ask a Spaceman!

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Episode Transcription (Auto Generated)

It was in 2006, in Prague, when the plot went down. The conspirators timed their plan well. They waited until the last day of the assembly when most of the voting members had left for home. They snuck in a draft document without sharing it with the people they knew would vote against it. In a rush, they called for a vote and made sure that they would have the numbers to support it.

Stunned and surprised, nobody could sound the alarm in time. Within a blink, the motion carried, the vote succeeded, and the conspirators would claim their prize. This was no mere coup d'etat. This was no overthrow of a government or secret installation of a dictatorship. No.

This was far more serious, much more far reaching, of much greater importance than some earthly power struggle. It was the new definition of a planet, one that would demote Pluto from the ranks of the planets of the solar system. You see, the conspirators were astronomers, and the assembly was a regular meeting of the International Astronomical Union. In Prague, well, Prague was Prague. We're not exactly sure what happened on that fateful August day in 2,006.

Well, we know what happened. Everyone agrees on the general outline. There was the IAU, International Astronomical Union meeting, and they vote on all sorts of things. The the general astronomical community, looks to this group as the one to name things and define things. So when the IAU decides something, it's generally viewed as the consensus will of the astronomical community.

And so this is what we end up putting in papers, in grant proposals. This is what filters through textbooks. They vote on stuff all the time. And on that day, in August in 2006, they voted on the definition of a planet. But that said, we have conflicting reports on the motives and maneuvering behind the scenes.

Some astronomers claim that there was indeed a conspiracy that an anti Pluto cabal worked in secrecy to develop a definition specifically designed to take away its planetary status, and that they arranged the vote in such a way as to blindside the pro Pluto camp. But other astronomers say that there was a healthy debate and dialogue, that a vote was on the agenda. It passed by simple majority just like thousands of other votes that nobody talks about. So why is this such a big deal? But before I dig into the vote and the definition of a planet, I'm sure there's a burning question on your mind right now, which is probably best summed up as who cares?

Seriously, why do we care so much about the definition of a planet? What does it change? Why does it matter? Isn't this just some yet another nerdy obsession for the nerds to nerd over? And well, yeah.

The definition of a planet isn't going to bring about world peace. It's not going to solve world hunger. It's not going to eradicate diseases. There are a lot of scientific endeavors that make the world a healthier place or a safer place or or more technologically advanced place that make our lives easier. And and astronomy is not one of those.

But astronomy is a branch of scientific research that makes the world a more beautiful place, and so that's why it's worth continuing. But I'm gonna be honest. The definition of a planet doesn't matter. It doesn't matter to us. It doesn't change your everyday life.

It doesn't change the outcome of any election. If we decide that Pluto is a planet or not, the only people that really care are the astronomers and the kids in grade school that we force to to memorize this stuff. But that said, within the astronomical community, we have plenty of good reasons to to care about the definition of a planet, in which solar system objects get to be on the list of planets and which don't. So it may not change the world, but it's going to change our world. For one, we've never had a definition before.

Legit. It's serious. We prior to 2006, there was no official astronomical agreed upon definition of the word planet. And we don't like to play loosey goosey in astronomy or science in general. We like to to have things nailed down, so it's about time.

Also, definitions reflect current understanding. So with a definition in place as a starting point, then as we update our information, as we learn more about the solar system, if we have a starting point of a definition, then we can modify that definition. But if we keep coming at this with a blank slate without any real definitions, then astronomers in this community are going to use this definition, astronomers over there are going to use that definition. Then as our knowledge evolves, it becomes harder to reconcile. And definitions help us sort things out professionally and programmatically.

What are you a specialist in? Are you a planetary scientist or not? That matters if if you're running an academic department and you're looking to make a new hire and you want to know, well, okay. We'll survey the people that we're doing. We'll get put them in some categories.

We got cosmologist over here. We've got a, supernova person over there. Oh, oh, do we have a planetary scientist or not? Well, let's look at what they study. Also, it's it's a matter of prestige and respect.

Are are you the person that discovered a new planet or a new category of solar system objects or just some schlub who found yet another small minor object in the solar system? When we decide on the importance of scientific advancements, definitions help us. And, of course, of course, the definition of the word planet matters because it all comes down to money. It always comes down to money. An object that is a planet is more likely to get funding in missions and studies because of the way human nature works.

When we say an object is a planet, then NASA is going to send probes there or rovers there. If it's just a a small, like, other kind of object in the solar system, we'll get to what those other kinds of objects in the solar system are. You have to fight for funding because, like, why would we send a spacecraft to some dumb rock when we could use that money to send the spacecraft to a real planet? The new horizons for example, the new horizons mission that went to Pluto launched in 2005. Alan Stern, the leader of that mission, who who argues to this day and will probably argue to his grave that Pluto is a planet, rather convincingly argues that if the definition had come before the launch of the mission, like, let's say, in the 19 nineties, we had defined a planet and demoted Pluto, new horizons probably would have never launched because we like to spend our money studying planets, not random rocks.

So there's this is important. So there were many good reasons that we should have had a definition for the word planet going back decades, but 2,006 was an especially right time. But to get into why 2,006 was the best time to do it, we need to rewind the clock a bit to, let's see. Let's see. Oh, right.

The same place that every astronomical discussion starts from, the ancient Greeks. Because that's where we get our word planet. It's from the Greek word planetos. This is they divided their sky into 2 kinds of objects. They had the fixed stars and the wandering stars.

There were stars that maintained their position night after night and season after season, and then there were stars that didn't. And this included the planets that we that they knew of like Mercury and Venus and Mars and Jupiter and Saturn. They didn't know about Uranus and Neptune because those were too dim for them to see. But it also included the sun and the moon to them. These were wandering stars.

These were planetos. These were planets. These were things that moved around the sky. And so we meet our first redefinition of the word planet. Again, unofficial.

No one's writing this down. It's not there's not not like the the the Greek astronomical union is sitting down and calling certain objects planetos or not. It's just like common usage that percolates through the millennia. And then we have a shift in the common usage with the Copernican revolution. You know, Copernicus, Kepler, Galileo, all those folks, and I need to do an entire episode, or I'm actually starting to cook up a series on the Copernican revolution and the Galileo affair that's gonna be tons of fun.

But that's a slow burn. That's like a background writing. Stay tuned for that. I'll get to it someday. But with the Copernican revolution, we redefined the word planet because the sun and the moon were planets.

They were wandering stars, wandering objects on the night sky. Now, when you reconfigure the solar system and you go from an Earth centered universe where everything wall revolves around that is some sort of star that revolves around the Earth. Now we have a sun centered universe, and then the Earth gets demoted or promoted depending on your point of view to the status of a planet. Earth joins the ranks of Mercury and Venus and Mars and Jupiter and Saturn. It's like those things that just orbits around the Sun.

The Moon gets demoted. It's no longer a planet. Now it's a satellite. And the Sun just becomes the Sun. It becomes its own unique category of things.

So so look at what what we have with the Copernican revolution. We start branching out our definition of planet, and we reclassify certain objects based on this reality. Instead of just a whole bunch of planets, we now have planets. Now Earth becomes a planet. The moon goes away from being a planet.

Now it's a satellite. The sun is no longer a planet. Now it's the sun. We've created a new categories of stuff. And this works fine for centuries.

I mean, of course, there are the comets and the comets are always gonna hang out being weird, and and they just always end up being in a category of their own. And then in the late 1700 early 1800, we start to discover more planets. We start with William Herschel discovering Uranus, and then Giuseppe Piazza discovering Ceres. Before I keep going though, I want to mention that this show is sponsored by BetterHelp. And, you know, New Year's is right around the corner, and I gotta tell you, New Year's resolutions are kinda stressful.

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Cool. New planets. We like this. We have better instruments, better telescopes. We're finding more wandering stars around the sun that in orbit, and, like, this is pretty fun.

We get to add more planets to the list of planets. But then in 18/02, Heinrich Olbers discovers Pallas with roughly the same orbit as Ceres, and all of a sudden, everyone's like, wait wait wait wait wait wait. Planets have orbits and orbits have planets. There's Mercury. It's right there.

It's not sharing that orbit with anybody else. Same for Venus. Same for the Earth. Yes. We have a satellite, but that's a satellite that goes around us while we go around the sun.

There's not like an a counter Earth on the opposite side of the solar system. Same for Jupiter. Same for Saturn. Same for newly discovered Uranus. But now we have Ceres and Pallas.

2 planets sharing an orbit, and this is getting weird. Few more years go by. 2 more objects are discovered in in this band between Mars and Jupiter, and people are starting to wonder if we should reclassify the word planet because it's it's starting to not make sense anymore. William Herschel himself recommends the word asteroid to describe these objects between or Mars and Jupiter. Other people stick to planet, but as the decades roll by, 100 more objects get found, and then everyone gives up.

And they're like, okay. We it doesn't make sense for a bunch of planets to share, an orbit with each other. There's this general sense that a planet is in control of its orbit, that there should be nothing else in its orbit. And here we have this belt between Mars and Jupiter that has a whole bunch of objects. No single object is in control or is consuming all the mass or clearing everything out.

So how about we call those a new thing? We call those asteroids and everyone kinda sorta goes along with that. Then in 1930, Clyde Tombaugh discovers Pluto, mostly beyond the orbit of Neptune, but sometimes not. Pluto is weird. Right away, Pluto is weird.

It's super small. It has a weird jinky orbit. It's at this, like, extreme angle unlike anything else. And almost immediately, people are saying, well, you look at Pluto. You look at the fact that it has a giant moon, Charon.

You look at the fact that it has this weird orbit and that it's super tiny. It doesn't really look like the other planets. It's like we have moons. We have satellites in the solar system that are way bigger than Pluto. So but everyone's like, well, okay.

Like, there's I guess, like, everyone has that weird cousin, you know, the weird member of the family that gets invited to all the functions, but, you know, doesn't quite fit in with everybody else, and but they're still part of the family. So we had this somewhat tense relationship with Pluto all the way up until the 19 nineties, and then things started to go off the rails in 1992. That's when astronomers discovered a small object at roughly the same orbit as Pluto, like, in the outer solar system. At first, they named it smiley, and some wondered if this should be a planet. Okay.

Do we have 10 planets now? Like, because it's not quite the orbit of Pluto. It's still pretty small. Like like, what are we doing here? This is a repeat of the early 1800 with the discussion of discussion of asteroids.

But if it's not a planet, no one really knew what it would be, what to call it. Like, they didn't have another word like asteroids at the ready. And so for a while, we just had these 2. We had, Pluto and then what would eventually be renamed, Albion, but I prefer smiley. And you should go to patreon.com/pmsutter so that we can launch a petition campaign to the International Astronomical Union and rename Albion back to smiley because that's way better.

I mean, who doesn't want a smiley in our solar system? That's patreon.com/pmsutter. But then just like the asteroids, we started to find more and more and more of these objects around Pluto. And I'm using the word around here very loosely. It's giant wilderness out there in the outer solar system beyond the orbit of Neptune, but there is definitely stuff out there.

But the real breaking point came in 2,005 when Mike Brown discovered Eris, an object sharing roughly the same orbit as Pluto a little bit further out, but even bigger than Pluto. Well, now we got a problem, don't we? Do Pluto and friends go the way of the asteroids, or do we expand the definition of a planet? Out of this debate, 2 camps emerge. One camp were called the geophysicists.

They said, look. A planet should look like a planet. We should base our definition of a planet based on what it looks like. And the number one thing that planets look like is round. And round isn't easy to get in the universe.

To be round, you have to be big. You have to build up enough stuff. You have to have enough mass, so you have enough gravity that pulls inwards and pulls you into a round shape. If you're too small, you don't have enough gravity and you can have any weird lumpy shape you want. Like, look at comets.

Look at asteroids. Those are obviously not planets because they're super round. So anything that is big enough to be round should be a planet. If it looks like a planet like you would picture in your head, that is a planet. And that would include Pluto, that would include Ceres, that would include Eris, and a whole bunch of others.

Those were the geophysicists. There's another camp, the dynamicists. And that word, I'm pretty sure is made up, but we're gonna go with it. The dynamicists, they cared less about what a planet looks like and cared more about what a planet does. And to them, a planet should clear its orbit going all the way back to this early 1800 notion of when we started to encounter the asteroids.

We're like, wait a minute. Maybe it should be 1 planet, 1 orbit. One orbit, 1 planet. A planet is an object that is able to dominate its orbit. It sucks up all the mass, all the available material in its orbit.

It clears it out. There's nothing left. It's in charge. It has its lane going around the sun, and there's nothing else in that lane. So in other words, the dynamic is, if an object acts like a planet like you would imagine a planet acting, 1 planet, 1 orbit, then that should be a planet.

And this definition would exclude Pluto and exclude Ceres because there's too much stuff sharing the orbit. This is why definitions are important. They help us clarify what processes and properties are useful and interesting and which are not. In this case, which is more important, What an object looks like or how an object behaves? Which is more critical to the definition of a planet?

This gets deep into the weeds of the role of planetary formation of when as a solar system is growing and all this material is gluing together to make different kinds of objects, planets, asteroids, comets, other. Different processes are going to lead to different outcomes, and processes could lead to, like, a Mercury or a Jupiter and other processes. And it's and it's an open question of whether it's the same processes that lead to things like Ceres or Pluto, or it's different processes, different evolutionary paths that give you a Ceres or a Pluto or an Eris that's different than a Jupiter or an Earth? We don't know. This is something we are still trying to figure out.

Is the story of solar system formation and the role of various physical processes and then how these end up into a solar system with the different kinds of objects that we see today. And the definitions help inform that and reflect that kind of knowledge. Do we define planets based on what they look like? Or do we define planets based on how they act? And what does that tell us of the history of the solar system itself?

So we needed to nail something down. In 2006, at the meeting of the IAU, after numerous discussions and debates between the geophysicists and the dynamicists, a proposal was offered to compromise. And the compromise became the definition, and that's what was voted on in that past. And that's how we get the modern definition of the planet, the one that was defined in 2006. In order to be a planet, you must satisfy 3 criteria.

1, you must orbit the sun. 2, you must be large enough that your own gravity makes you nearly spherical. And 3, you must clear your orbit. You'll notice that this compromise means that the dynamicist actually won because it's the 3rd criteria that kills Pluto. Pluto orbits the sun.

Check. 2, Pluto is large enough that its own gravity makes it nearly spherical. Check. Pluto is not big enough to clear its own orbit. There's too much stuff out there.

In other words, Pluto may look like a planet, but it's not acting like a planet, which explains why Pluto is the weird cousin. They don't quite fit in the family, and then you do a DNA test, and it turns out they're actually not related to you at all. And you're like, oh my gosh. We don't have to invite them to the the family events anymore. But the compromise means the dynamicist won.

So, of course, everyone just accepted this as a legitimate vote of the IAU and moved on with their lives. Of course, I'm kidding. The fighting has not stopped, and the vote has not 100% settled the matter. Opponents of the definition say it's frankly not a great definition for planet, and they kind of have a point. And there are weaknesses with the IAU definition.

1, are you seriously telling me there are literally only 8 planets in the entire universe? Like, really? Because the first definition is it must orbit the sun. So, yes, we know of exoplanets, planets orbiting other stars, but we're creating an entire category of object in the entire universe, which contains 100 of billions of stars in each galaxy and, you know, trillions of galaxies in the observable universe. And in throughout the entire expanse of space and time throughout the history of the cosmos, there are 8.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. That's it? Like, we're going to make an entire category of astronomical object that has 8 members. And then even moving beyond that, like, the definitions of nearly spherical and cleared its over orbit are super fuzzy. How do we define sphericalness?

What is the threshold? No planet is perfectly spherical. And then the definition says, well, it has to be nearly spherical. Well, how much? 10%, 1%, point 001%.

I mean, come on. I thought we were astronomers here, and the whole point of a definition was to nail things down and remove ambiguity. And now your definition literally has ambiguous phrasing and then cleared its orbit. This is even fuzzier. This is the only time we define an object based on its environment, not something intrinsic to the object itself.

And people point out, if you were to take Earth and move it to the orbit of Pluto, then all of a sudden, Earth doesn't get to be a planet anymore. And if you were to take Pluto and move it to the orbit of the Earth, then Pluto gets to be a planet. That seems weird. Doesn't it? On the other hand, supporters, proponents of the definition have some valid counterarguments.

Like, yeah, there are only 8 planets. Like, deal with it. 2, have you ever, dealing, you know, regarding this nearly spherical, nearly round thing? Have you ever seen a planet? They're obviously round.

And, yes, the definition is fuzzy, but planets are really, really, really, really, really round. Like, you will look at it and you say, that's a round thing. Even something like Saturn where it's a little little squishy, little fat around the middle, you say, that's a round thing. That's a nearly spherical thing. I can eyeball it.

And then you look at an asteroid or a comet, you look at those and you say, those are those are not round things. So there's no point in quibbling over the percentage threshold or the second decimal place or whatever because planets are obviously round and not planets are obviously not round. And then the whole clearing the orbit thing, yeah, it's true that if you moved Earth to Pluto's orbit, it would be demoted. And if you moved Pluto to Earth's orbit, it would be promoted. But Earth ain't out there, is it?

Obviously, something happened in the inner solar system at this distance 93,000,000 miles from the sun. Something happened here at this orbit that didn't happen at the orbit of Pluto. And so our definition of planet includes it folds in the formation history of these objects, not just their placement and not just their appearance, but the processes that led to them to be what they are today. And check this out. Yeah.

There's all sorts of junk in the solar system. We have tiny little rocks that follow us in our orbit. Every single planet does, but it's a different scale. Mars Mars is 5 1,000 times more massive than the next largest thing in its orbit. 5000 times more massive.

Pluto Pluto only captures 7% of the total mass in its orbit. And you look out there at the orbit of Pluto, the the environment around Pluto, the orbit of Pluto is not dominated by the gravitational, you know, sway and power of Pluto itself. No. It's all dominated by Neptune, the real planet. That's the one who's in charge out there in the outer solar system.

Its gravity affects everything else out there, the, around the orbit of Pluto. But you look at the orbit of Mars, and Mars is in charge. So, yeah, we can get away with a fuzzy definition because there's this huge discrepancy in terms of clearing the orbit between the planets and the non planets. Still, the the arguments have gotten even pettier. Some astronomers even accuse the dynamicist of a of a legitimate conspiracy arguing that of the roughly 10,000 astronomers in the world, less than 500 were present for the vote.

So that's hardly representative of the community's views. Some even say that over the course of that IAU meeting in Prague, there was a big anti American vibe backing this as because, you know, planetary science is dominated by the United States because we have NASA. We have the spacecraft. We have the space probe. You know, it was American that discovered Pluto.

It was American that discovered Eris. You know, and so, like, planetary science is a very American thing, and so may there was this anti American vibe, especially in response to the war in Iraq. But like I said, the astronomers who got this through all said that everything was on the up and up, and this is how meetings work and voting's work. And if you didn't wanna show up to vote, you can't be mad at the outcome. So there might have been shenanigans at that meeting.

It's a little unclear, and we'll just leave it at that. And I know I did an episode on this years back. In fact, I think it was my second episode of all time. And in that episode, I came down firmly in favor of Pluto being a planet. Since that time, I've softened a little in my old age, and I've come to realize that we actually have no good definition at all.

That no matter what we come up with, there are going to be shortcomings, and there are going to be confusing things. And I mean, in all honesty, the current definition and categorization of the object in the solar system is a bit of a mess. The mess isn't necessarily in the definition of a planet. I can I can honestly see both arguments, both sides? The geophysicist and the dynamicist.

I I can see it. Like, there there's a healthy worthwhile debate there about which object should be planet planets and which should not be planets. My problem with the current IAU definition is is the categorization of literally everything else. Because besides the planets, there of which there are only 8, we have a bunch of other objects. We have the and and it's in these categorization of the other objects that things get really, really head confusing.

For example, we have the satellites, which are any objects that orbit around the planets. Okay. And in this case, we have some obvious ones like the moon or Titan or Europa. But then when we go out and say, like, oh, Jupiter has, like, 70 moons, and it turns out most of them are tiny rocks, you're like, does that count? Right now, they do.

We also have the comets. Okay. Okay. Comets have always been weird. Category, unto themselves.

Then we have the, quote, minor planets, which is no joke, everything else that isn't a planet, a satellite, or a comet. So if if you look at yourself, you look at your name tag, and you don't have planet, satellite, or comet on that name tag, you are a minor planet. But it doesn't stop there. If a minor planet is large enough to be round, like Pluto, Eris, Ceres, a few others, then it is called a dwarf planet, which is a subcategory of minor planets. So basically, if you follow the, the first two if you check off the first two criteria of the definition of planet, you orbit the sun and you're big enough to be round, but you're not big enough to clear your orbit, then you are a dwarf planet.

But this is different. We use the word dwarf a lot in astronomy that we have, like, dwarf galaxies, dwarf stars. But in those cases, we understand that a dwarf star is still a star, just a smaller version of it in contra to a giant star. And same thing for a galaxy. We understand a dwarf galaxy is just a galaxy that's on the small end.

That's it. It's a subtype, but it still gets to be a galaxy. A dwarf galaxy is still a galaxy. A dwarf star still gets to be a a star. But a dwarf planet is not a planet.

This is emphatic. Like, here, like, a dwarf planet is not considered the small end of the spectrum of what planets could be. It's considered an entirely different category of its own. Contrast that with the giant planets. You know, Jupiter, Saturn, Uranus, and Neptune.

We understand giant planets to be a category, a kind of planet. And we have terrestrial planets which are a kind of planet. But dwarf planets, uh-uh. They're not a kind of planet. They're their own thing, which means we probably should have given them their own name.

Like, William Herschel invented the word asteroids. We need a new name, but we don't. It's dwarf planet, but it doesn't mean it's a subtype of planet. I'm sorry. If it's not large enough to be round, then it's called a small solar system body.

Alright? So if you orbit the sun, but you're not big enough to be round, then you are a small solar system body. But comets, which have their own category, are now also lumped in with small solar system bodies, so there's an overlapping definition. Some minor planets are small solar system bodies, but not all minor planets because some of the minor planets are dwarf planets, and all the comets are now also small solar system bodies. What about the asteroids?

Why then I use that word? Well, that's never been officially defined, And it's used generally nowadays to refer to small solar system bodies of the inner solar system which is a bit of a mouthful. And there are some new definitions on the block. We've got trans Neptunian objects which are anything beyond the orbit of Neptune which includes most of the comets, Pluto and its friends, and some of the small solar system bodies. And we also now have the Plutoids which are objects like Pluto at its orbit or beyond.

All plutoids are minor planets and they're also all dwarf planets and they're also trans Neptunian objects. So if you are a minor planet, a dwarf planet, and a trans Neptunian object, you are a plutoid. But not all trans Neptunian objects are minor planets because it includes some of the comets. Oh, and by the way, some trans Neptunian objects are also satellites because why not? I don't know about you, but I would say that's a bit of a mess.

There are a lot of categories and subcategories which is fine, but there's also partial overlap of the subcategories where things, in my opinion, get weird. Where an object can belong to multiple categories, depending on where it's placed in the solar system or how it behaves. And they're like these complex diagrams with, like, overlapping circles to to describe the various kinds of objects in the solar system. And and I understand the motivation. The creators of this definition were trying to take our most up to date understanding of the solar system and make it work with colloquial definitions that built up over centuries, which is no easy task.

Plus, our solar system is generally a messy place anyway, especially in the outer regions with that we are just beginning to understand with what appears to be a wide variety of objects in a wide variety of orbits with a wide variety of behaviors. So maybe real life is just a mess and our definitions are going to reflect that. So while I'm tempted to say that we need a new definition of a planet and that we need to clean all this up, I'm worried that what will come out of this process will be an even nastier mess. Because since 2006, many other proposals have come out of the woodwork and they're they're all kind of stupid in their own unique ways. There are proposals out there to say, label anything roundish a planet.

If it's big enough to pull itself together with its own gravity, it's a planet. That includes satellites. Like, the moon would become a planet, but this becomes what would be called a satellite planet which is, weird. There's a proposal out there that anything orbiting the sun at least the size of Pluto should be a planet, which is just totally arbitrary and leans on sentimentality and not, like, actual physics. There's a proposal to rename the planets as Uber planets and the dwarf planets as unter planets which doesn't solve anything.

It just makes it German. And there's my personal favorite because it's so bad. It's to rename planets as plunars and stars as fusars. Fusars are objects capable of fusing nuclear fusion in their cores. And then if you are can't do that, then you are a planar.

I don't it's we're just making up words here. William Herschel did a best with asteroid, and no one's been able to beat him in 200 years. Not to mention the issue with exoplanets, rogue planets, double planets, brown dwarfs, the line between all that. Maybe the universe is just messy, and our definitions are always going to be messy and confusing. And there's healthy, legitimate debate between what should be a planet and what should not be a planet.

And then once you decide, once you make your cut off of planet, however you define that, There's going to be a whole bunch of other stuff. And I don't think we've quite nailed how to define all that other stuff and how to categorize it because we're still learning. So I think that's my final verdict. Let's give it all a break for, say, another century. Let's see if we've learned some new things, and then hopefully, we can come to a decent decision later.

Thank you to Manasa a at I'm on my level and Miguel v for the questions that led to today's episode. And thank you so much to all my Patreon contributors. That's patreon.com/pmsutter. And I'd especially like to thank my top contributors this month. Justin g, Chris l, Hiberto m, Duncan m, Corey d, Stargazer, Robert b, Nyla, Sam r, John s, Joshua, Scott m, Rob h, Scott m, Lewis m, John w, Alexis, Gilbert, m, Rob w, Dennis a, Jules, r, Mike, g, Jim, l, Scott, j, David, s, William, w, Scott, r, Heather, Mike, s, Michelle, r, p h, Steve s, Watt Wotburg, Lisa Arcusi, and Kevin b.

Thank you so much. Please keep those questions coming. That's AskASpaceman@gmail.com or the website AskaSpaceman.com. Keep sending in those reviews on iTunes and Spotify. They help grow the show's visibility so I get more questions and you get more answers, and I will see you next time for more complete knowledge of time and space.

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