G'day, Dillon O'Donnell here. Remember when Pluto was demoted or reclassified as a planet? And every pseudo-intellectual thought it made them look really smart. If they pointed that fact down to you, if you ever incorrectly referred to it as a planet. You asked them if Pluto's a planet, didn't you? No! It's not shut up! Remember when kids' toys were redesigned? Postes were reissued. Textbooks were rewritten all to exclude Pluto because of this new classification. And all of this was happening while we had a spaceship on the way to Pluto. Which got there, took lots of amazing photos, sent them back to Earth and we all looked at it and went, hmm, that's a pretty good looking planet. Well, I'm here to explain to you why the International Astronomical Union's decision is highly contentious. Not just among people who had some emotional, historical connection to Pluto being a planet, but in the science community as well. It's not a cut and dry decision and it's something that people like Jerry maybe had right the whole time. Pluto was a planet, some committee of fancy assholes disagree, I disagree back. My name is Dylan O'Donnell and you're watching Star Stuff. Let's be clear. Pluto doesn't actually care what we call it. The universe is complicated. It's like species. Sometimes we classify them as species or subspecies and scientists argue about this definition too. But at the end of the day it's a long, complicated gradient of objects that lie right on the boundary. Science is reductive and we do like to reduce things into nice classifications. But the question is, can we do this so that we have some sort of scientific utility with the data we collect? If you are a scientist trying to find life, perhaps you want to make a list of places you can detect phosphine in the solar system and you run a database query to say show me all the planets. If you were only searching for planets as defined by the IOU, you would leave off Saturn and Jupiter's moons. Interesting moons like I.O., Europa, Titan, you would also leave off Pluto, series and a whole bunch of other really interesting places that you should be searching for life or a detection of phosphine or whatever your scientific inquiry is. Having this definition of a dwarf planet or a non-classical planet doesn't actually help the science whatsoever. In fact, if you do a Google scholar search for the term dwarf planets, you'll find that all of the papers relate to M-dwarf stars. Scientists don't actually use dwarf planet as a useful classification for study. The vote in Prague where this all went down was weird. At the end of that vote in 2006, it was decided that a planet should be a body that is in orbit around the Sun has sufficient mass for its self-gravity to overcome rigid body forces so that assumes a hydrostatic equilibrium nearly round shape and has cleared the neighborhood around its orbit. Now it wasn't just one vote, there was a series of votes. Now if this is something to bear in mind, that conference had thousands of astronomers there but the vote only included a few hundred votes. There was another resolution on top of that definition that then introduced the term dwarf planet or a non-classical planet. In the end, the vote was 237 versus 157. It was really close. So this is pretty far from scientific consensus. It's also argued that at the end of this 10-day conference, most of the important or working astronomers had already left. So the vote was left to the few people who at the time to actually sit down and consider the motions. But this new definition of a planet is broken. It talks about a planet having to be in orbit around the Sun. Now this instantly precludes all exoplanets. It doesn't address brown dwarf stars. It would immediately exclude row planets. For example, if Earth suddenly got kicked out of the solar system by some gravitational force, Earth would suddenly not be classified as a planet anymore. Even though it is a planet, it's just not going around the Sun. It's a weird thing to include in the definition. And this whole idea about considering its orbit, now that one of the reasons Pluto was demoted was because it has a Barry center which is in between Sharon and Pluto. In theory, you could have planets as large as Jupiter spinning around each other. Under the new IAU definition, neither of them be considered planets. It's almost like if you were a caveman sitting down with your friend and a bear attacked you, and you fend it off the bear, and you said to your friend, that was a strange animal, wasn't it? I'm glad it's gone. And then your friend's looking at it going over the horizon and goes, you know what? Now that it's far enough away from the cave, it doesn't look that big. I don't think we can call it an animal anymore. The next nail in the coffin for this definition is that scientists don't actually use it. If you take a few moments to go to Google Scholar, some papers will specifically mention Pluto was classified as a dwarf planet, but in their usage and their verbiage as they write their papers. The next nail in the coffin for this definition is the most accurate one, but it's not the most accurate one. The next nail in the coffin is the most accurate one. Planetary dwarfism actually has nothing to do with size. At the end of all of this, you would have assumed that the reason a planet like series or Pluto gets reclassified as a dwarf has something to do with their size. Maybe there's a number somewhere. There isn't a number. And it really feels like it was targeting Pluto. Some committee of fancy assholes disagree, I disagree back. But I'm not just going to sit here and winj about it without giving you an alternative. And there have been alternative definitions proposed. This vote will come up again in future. And especially as we learn more about exoplanets, astronomers are going to have to come to terms with the definition that actually is useful. And the one that I prefer is the geophysical planetary definition. It reads like this. A planet is a substellar mass, so not a star that has never undergone nuclear fusion. And that has sufficient self gravitation to assume a spiroidal shape, regardless of its orbital parameters. It's pretty simple. If it's not a star, but it's big and round and floating around in space, it's a planet. So let's talk about this one more way. Talk to those objects or dogs, aren't they? They're very different in size. It's not about whether the Chihuahua isn't a big herd of Chihuahua's or in any group of dogs. It's not about whether the big guy is in a group or not. Typically in science, normally in science, we classify species, geological formations, and other objects in space by their own attributes with nothing engineered to limit the number. I think that the IOU made a tragic mistake, and I'm going to stop right there, and I'd like to hear Ron's Rebellion. Thank you. And whoa! I don't care what anyone says. If it can be a planet, it can be a planet again. Planet, planet, planet, planet. I hope you enjoyed this monomant. So the next time someone tries to talk smarter than that, actually, ah, by telling you that Pluto is not a planet, maybe try telling them that it is a planet, and it will be a planet again. This is far from over. Let's all take a moment to look at planet Pluto, not just an interesting round rock in space, but an active landscape with mountains and valleys and glaciers that rival the ones that we have right here down on Earth. Another planet. I hope your astronomy journey is going well. My name is Dylan O'Donnell. You've been watching Star Stuff. Remember, everything is meaningless, and we're all going to die.