Unveiling Pluto, with Alan Stern and Neil deGrasse Tyson

Two prominent voices in the “Planet vs. Dwarf Planet” debate, Alan Stern and Neil Tyson, discuss what New Horizons has uncovered about our favorite Kuiper Belt object. In studio, astrobiologist Dr. David Grinspoon and Chuck Nice join the fun.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:14Neil deGrasse Tyson?

  This is StarTalk, and I'm your host Neil deGrasse Tyson, your personal astrophysicist. And I'm also the director of New York City's Hayden Planetarium at the American Museum of Natural History. My co-host today is Chuck Nice.

• 0:27Chuck Nice?

  Yes.

• 0:27Neil deGrasse Tyson?

  Chuck.

• 0:28Chuck Nice?

  Hey Neil.

• 0:28Neil deGrasse Tyson?

  Looking good, got your NASA uniform on.

• 0:30Chuck Nice?

  That is correct, sir. I am wearing a NASA shirt.

• 0:33Neil deGrasse Tyson?

  NASA t-shirt, very good, trying to get good with me. You don't need to do that, I love you no matter what.

• 0:37Chuck Nice?

  I appreciate it, man, I really do. Actually, when I cover, I'm wearing a shirt over top of the shirt, and I have to make sure that the "N" stays visible.

• 0:46Neil deGrasse Tyson?

  Otherwise it looks like "Assa." Okay, fine.

• 0:49Chuck Nice?

  Which for some reason makes sense when I wear it!

• 0:53Neil deGrasse Tyson?

  Today, we're talking about Pluto, and the farthest reaches of our solar system. There's a lot of stuff out there. Featuring my interview with Mr. Pluto himself, Alan Stern.

• 1:03Chuck Nice?

  Yes.

• 1:04Neil deGrasse Tyson?

  He's a friend and colleague, he's the principal investigator, the PI of NASA's New Horizons mission to Pluto.

• 1:11Chuck Nice?

  That's right.

• 1:11Neil deGrasse Tyson?

  He's also a planetary scientist at the Southwest Research Institute in Boulder, Colorado.

• 1:16Chuck Nice?

  It's no Hayden Planetarium, I'll tell you that.

• 1:18Neil deGrasse Tyson?

  No stopping.

• 1:19Chuck Nice?

  Just saying.

• 1:20Neil deGrasse Tyson?

  Actually, Boulder, Colorado, they have the real sky.

• 1:22Chuck Nice?

  Yeah, they do, they don't, no noise pollution there, no light pollution.

• 1:25Neil deGrasse Tyson?

  Light pollution, exactly.

• 1:26Chuck Nice?

  No light pollution.

• 1:27Neil deGrasse Tyson?

  Now, people know my history with Pluto, and just in all fairness to that, I had to bring on somebody who's a Pluto sympathizer.

• 1:35Chuck Nice?

  And it was awesome.

• 1:36Neil deGrasse Tyson?

  Who's also an expert on the solar system.

• 1:38Chuck Nice?

  And it was great.

• 1:39Neil deGrasse Tyson?

  We're gonna bring in planetary scientist David Grin spoon. David, where are you? Hey there. Oh, hey dude!

• 1:48Neil deGrasse Tyson?

  Your Twitter handle is DrFunkySpoon, which I, every time I hear, I gotta like recite it. Funky Spoon.

• 1:53Chuck Nice?

  Dr. Funky Spoon.

• 1:54Neil deGrasse Tyson?

  You're a senior scientist at the Planetary Science Institute, and where's that?

• 1:58David Grinspoon?

  Well, Planetary Science Institute is in Tucson, but I'm actually in Washington DC. Uh, we're sort of a distributed beast, the Planetary Science Institute. We have, uh, members all over the world and I'm here, uh, I'm part of the Washington outpost.

• 2:12Neil deGrasse Tyson?

  Okay, cool. And you study comparative planetology, which is cool. This is where you see what planets have in common and what differs among them. You're a particular expert on icy moons and Mars and Venus. You wrote a book on Venus, I remember, correct? I think I own that book. What was that one?

• 2:27David Grinspoon?

  Yeah, yeah, Venus Revealed. I love Venus because it's so much like the Earth and so much unlike the Earth. It's both, you know, it's a, it's a mystery.

• 2:36Neil deGrasse Tyson?

  You said Venus Revealed. It might have been a better title, Venus Unveiled.

• 2:40Chuck Nice?

  Hmm.

• 2:41David Grinspoon?

  Yeah.

• 2:41Neil deGrasse Tyson?

  Then you get the double, you get the double.

• 2:43Chuck Nice?

  Double entendre going on there, seeing as how Venus, the de Milo and, you know.

• 2:48David Grinspoon?

  Maybe the next edition I'll go for the unveiling.

• 2:51Neil deGrasse Tyson?

  Okay. So, and also you care about Pluto and you're, I, I'm told you're working on a new book with Alan Stern. What's that one called?

• 2:58David Grinspoon?

  Yeah, I, boy, I love Pluto and Alan and I are, uh, working on a book called Chasing New Horizons.

• 3:04Neil deGrasse Tyson?

  Oh, okay.

• 3:04Chuck Nice?

  Okay. A little word play there. New Horizons, the mission and great, chasing.

• 3:09Neil deGrasse Tyson?

  And when does that come out?

• 3:10David Grinspoon?

  It comes out next year, twenty, 2017.

• 3:12Neil deGrasse Tyson?

  Nice, okay. We'll look forward to that. And, and by the way, you are one of our newly knighted StarTalk All-Stars. Congratu- thank, uh, I'm saying congratulations, but it's up for you to say whether you want to be that or not.

• 3:23David Grinspoon?

  Oh, I very much want to be. I'm really excited to be a, a StarTalk All-Star. I had a blast, um, at, at our launch party and, um, recording the first few episodes. I'm looking forward to doing more.

• 3:35Neil deGrasse Tyson?

  Excellent. And this is not your first time on the air with us. So it's great having you. So what, tell me about New Horizons. It already passed by Pluto, right? When did that happen?

• 3:44David Grinspoon?

  Yeah, it happened just about a year ago, or approaching a year ago, on, um, July 14th, 2015.

• 3:52Neil deGrasse Tyson?

  Okay.

• 3:52David Grinspoon?

  Uh, it was a, it was a long time coming and.

• 3:55Neil deGrasse Tyson?

  So David, David, I remember growing up and every planetary encounter was a flyby. And that word was part of our culture. Then we got a little more expensive with our spacecraft and they carried extra fuel and they could pull up, slow down and enter orbit. So no one used the word flyby, it seems, for decades. So why didn't we pull it, slow down and pull into orbit around Pluto so we can hang out there? Why did everything have to focus down into just a few seconds of close-ups and then the thing overshoots? And it's lost in the Kuiper belt.

• 4:25Chuck Nice?

  Like George Bush over Katrina.

• 4:28David Grinspoon?

  Yeah, right. We're doing a heck of a job. No, it's, I mean, you're right. You're right to relate it to that history because the reason why our first missions to Venus and to Mars and to Jupiter were flybys is because it's easier to do a flyby. You don't have to take another big rocket and all that extra fuel with you to slow down when you get there to go into orbit. And Pluto was really hard to get to because it's so darn far away. And, you know, we were lucky to be able to do a flyby to, you know, we had to launch a really fast rocket. Throw everything we we had at it, basically, just to get a very small spacecraft there.

• 5:03Neil deGrasse Tyson?

  And even so, it took how long? Even so?

• 5:05David Grinspoon?

  It took nine years.

• 5:06Neil deGrasse Tyson?

  Nine years. Now, I I I've tried to spread this fact far and wide.

• 5:10David Grinspoon?

  Right.

• 5:10Neil deGrasse Tyson?

  That the first rule of any science experiment is that it needs to be completed before you die.

• 5:18Neil deGrasse Tyson?

  So is that is that fair enough, David? Is that a fair enough first rule?

• 5:22David Grinspoon?

  Well, I think it's a good rule. I it would be, it's going to be challenging for, you know, some of the things we would like to do in the future, like getting to the exo-planets unless we greatly expend our extend extend our life expectancy. But, yeah, I tend to favor projects that I might have some chance of seeing to completion.

• 5:38Neil deGrasse Tyson?

  So so you put some awesome rockets on what is otherwise a relatively light space probe, and it gets out there very fast. You get high acceleration, right?

• 5:46David Grinspoon?

  Yeah, and then we also had to do a Jupiter flyby to further accelerate. Uh, yeah, amazingly, New Horizons took one year to get to Jupiter. I mean, think of how fast that is.

• 5:56Neil deGrasse Tyson?

  Wow.

• 5:57David Grinspoon?

  You know, all our Galileos and Voyagers, they took years and years. New Horizons got to Jupiter in basically one year and then picked up even more speed with the Jupiter gravity.

• 6:06Neil deGrasse Tyson?

  Just to be clear, you stole some of Jupiter's orbital energy and gave it to New Horizons. Just confess that.

• 6:12David Grinspoon?

  We pilfered a little bit of momentum from Jupiter. I don't think Jupiter's gonna care, but it really helped us out a lot.

• 6:19Neil deGrasse Tyson?

  So we'll we'll get back to that in a minute, but just some facts about Pluto, named for the god of the underworld, right?

• 6:25Chuck Nice?

  And here, and all this time I thought it was the dog. I am, I can't believe that.

• 6:30David Grinspoon?

  Yeah, a little, a little bit morbid. And you know, there was a bit of a controversy because there was one idea that all of the features on Pluto should be named after things having to do with death and the underworld. Like every feature on Pluto should have something to do with death. And other people said, well, that would be really pretty morbid. Why don't we name features on Pluto after, you know, spacecraft and scientists and gods and, you know, people that had something to do with Pluto.

• 6:58Neil deGrasse Tyson?

  I vote for death.

• 7:01Chuck Nice?

  That is so much cooler.

• 7:02Neil deGrasse Tyson?

  That's way cooler.

• 7:04David Grinspoon?

  Yeah, but an entire planet just devoted to death? I don't know.

• 7:08Chuck Nice?

  Uh, hey, listen, it worked for Darth Vader.

• 7:11Neil deGrasse Tyson?

  Wait, just, just, just, by the way, he slipped in the fact that he called it an entire planet. Okay. Just kind of reminds you who you, who, who, just kind of reminds you. By the way, uh, just, what is the mass of Pluto relative to Earth's moon?

• 7:24David Grinspoon?

  Pluto is really, really tiny for a planet and, or for a object that some people might call a planet. And it is in fact only about a sixth the mass of Earth's moon. So it's really, uh, you know.

• 7:39Neil deGrasse Tyson?

  Okay. So just, just fess that up.

• 7:41Chuck Nice?

  I know what you're saying, man. Listen, even a micro penis is a penis.

• 7:46Neil deGrasse Tyson?

  Time to throw to the clip.

• 7:49David Grinspoon?

  Wait, I thought, I thought that was called a dwarf. Uh, nevermind.

• 7:54Neil deGrasse Tyson?

  So Alan Stern came to town and I sat down with him, catch up on New Horizons flyby of Pluto. Let's check it out.

• 8:02Neil deGrasse Tyson?

  What a year it was for New Horizons. Oh my gosh. Just, I want to say congratulations. My gosh.

• 8:07Speaker 03

  Oh, thanks a lot. You know, New Horizons is a huge team of people. Actually over 2,500 people worked to build it.

• 8:12Neil deGrasse Tyson?

  Oh my gosh. And what center, what institutions were?

• 8:15Speaker 03

  It's a joint project funded by NASA, but a joint project of the Southwest Research Institute, the Johns Hopkins Applied Physics Lab. Lots of big partners in it and also small and large corporations, everybody from Lockheed and Boeing.

• 8:27Neil deGrasse Tyson?

  Somebody's got to build the spacecraft.

• 8:28Speaker 03

  And all the instruments and the ground system, mission control, all of it.

• 8:32Neil deGrasse Tyson?

  And so I'm going to ask you like cliche questions, like what most surprised you arriving at Pluto?

• 8:38Speaker 03

  Two things. One was. Just how stunningly complex the Pluto system is compared to our expectations. And secondly, the viral public response, just loving the exploration, just people, a billion web hits, 10 times anything NASA had ever seen, 450 newspaper covers above the fold on a single day, every continent on Earth, even Antarctica.

• 9:01Neil deGrasse Tyson?

  So the Antarctica Daily News.

• 9:03Speaker 03

  Exactly, I got a copy of it, it's not called that, but yes, they sent it to me from the pole. The one and only news, I says every continent but Antarctica on a radio show, and the Antarctica people got all upset, we covered it.

• 9:16Neil deGrasse Tyson?

  So, and I have to agree, not that I had any professional expectations for it, because I don't study planets professionally, but to see the images and the nuance and the detail, I was fully expecting it to be some pockmarked victim of whatever hits it, you know, and then it's just that. But it had an entire surface personality that could not be explained by just things hitting it. And so I was delighted.

• 9:43Speaker 03

  Yeah, you know, we see canyons, we see glaciers, we see evidence of potentially former liquids that ran on the surface. We see really varied terrain, it's like out of a sci-fi novel, thousand-foot-high methane crystals that run for hundreds of kilometers.

• 9:59Neil deGrasse Tyson?

  So does this tell you that Pluto was ge- Pluto-ologically active, is there a word for ge- the geology of Pluto?

• 10:06Speaker 03

  Very clearly.

• 10:07Neil deGrasse Tyson?

  But it seems so little, and we don't think of tiny objects as having active geology.

• 10:12Speaker 03

  That's right, but...

• 10:13Neil deGrasse Tyson?

  Is that a bias?

• 10:14Speaker 03

  It's a bias. The less planetary sciences, we get surprised when we go to new places, this is the first time we've been to a dwarf planet, and guess what we discovered? It's a lot more complicated than anybody expected. There's a place we call Sputnik Planum on Pluto, it's a big ice field, it's a thousand kilometers long, it's a million square kilometers, we can't find one crater on it, and we've age-dated it from that, and it can't...

• 10:36Neil deGrasse Tyson?

  So in other words...

• 10:37Speaker 03

  It was born yesterday.

• 10:38Neil deGrasse Tyson?

  Yeah, in other words, you age-date because you have some expectation of what rate craters would accumulate.

• 10:44Speaker 03

  So it's sort of like we know how hard it's raining, and you can say, well, this piece of paper has that many dots, how long has it been out there?

• 10:50Neil deGrasse Tyson?

  Good.

• 10:51Speaker 03

  Versus some other piece of paper with more or less dots.

• 10:52Neil deGrasse Tyson?

  And so that paper would have been out there longer, right?

• 10:55Speaker 03

  Yeah, and in the case, Sputnik Planum is the scale of the state of Texas, and it was created yesterday geologically.

• 11:01Neil deGrasse Tyson?

  Whoa. Whoa.

• 11:04Speaker 03

  This little planet is somehow active after four billion years.

• 11:06Neil deGrasse Tyson?

  Any understanding of that?

• 11:08Speaker 03

  Nope.

• 11:08Neil deGrasse Tyson?

  Okay, so, so, so what people don't understand is scientists love being stumped.

• 11:14Speaker 03

  We love being stumped and we, we don't mind being wrong. Like, we thought Pluto would be simpler. We were wrong. This is wonderful.

• 11:21Neil deGrasse Tyson?

  David, so you're planetary comparative planetologist, right? And so, so how would you compare Pluto's features to other stuff going on in the solar system? I, I didn't see, I, I didn't notice anything like it out there, but you, you've got a better mental inventory.

• 11:36David Grinspoon?

  It's marvelous. I mean, you know, I'll admit to having some anxiety that in addition to just wanting the darn thing to work after all those years, I had some anxiety that maybe Pluto would be boring after all. It's, you know, it's, it's, it's small. Maybe it'll just be full of craters and not that interesting. But in fact, it's anything but. And there are, uh, features that are reminiscent of many other places. And yet there are aspects that are just all, you know, pure plutonium and, and nothing like it. Uh, you know, maybe the most similar place is Neptune's moon Triton, which is around the same size and, you know, also a frozen outer solar system object that's largely composed of nitrogen ice.

• 12:15Neil deGrasse Tyson?

  So are you saying they look, they look alike or they actually, oh, so you've got some chemistry analysis of what's going on on the surface?

• 12:21David Grinspoon?

  I'd say that, you know, there's some similar features, um, but it's not like you would mistake one for the other.

• 12:27Neil deGrasse Tyson?

  But you have nitrogen ice, that's frozen nitrogen, I guess. What else, what else you have?

• 12:31David Grinspoon?

  You got nitrogen ice, you've got traces of methane.

• 12:33Neil deGrasse Tyson?

  Methane ice?

• 12:34David Grinspoon?

  Yes. And, and, um, also you have some features, uh, on Triton that are probably, uh, that are surely water ice. You know, the sort of bedrock, the strong stuff on Pluto and also on Triton is water ice, kind of playing the role that, that bedrock, that rock plays.

• 12:51Neil deGrasse Tyson?

  So just to be clear, so nitrogen ice, we know nitrogen, that we breathe that in our atmosphere. Methane is the gas that most people in urban centers would use in a gas stove.

• 13:01Speaker 03

  Right.

• 13:01Neil deGrasse Tyson?

  So you're cooking with gas?

• 13:02Speaker 03

  Cooking with gas, right? It's also the gas that we make ourselves.

• 13:05Neil deGrasse Tyson?

  Uh, oh, yeah, yeah, out of, out of, out of your butt.

• 13:09David Grinspoon?

  I was gonna say cows.

• 13:12Neil deGrasse Tyson?

  Cows, okay, fuck, cows, yeah, comes out of their digestive.

• 13:16David Grinspoon?

  Not ours, right, right. Exactly. It was a cow.

• 13:20Neil deGrasse Tyson?

  So, so, but methane, we, we're familiar with it as a gas, and you're saying it's methane ice, which means it's not only cold enough to liquefy the gaseous methane, it's cold enough to solidify liquid methane. What temperature is that?

• 13:35David Grinspoon?

  It's, oh, gosh, minus two hundred, I don't remember the exact.

• 13:41Neil deGrasse Tyson?

  Okay, so.

• 13:41David Grinspoon?

  Really cold, really cold. But it's, it's pretty darn cold.

• 13:44Neil deGrasse Tyson?

  Yeah, you could have just said darn cold, and that would have worked perfectly for us. So, there are also, beyond what the chemistry is, there are surface features that are intriguing, one of which people illustrated with a Valentine-shaped heart. And so, what is accounting for these bright and dark areas and these, these different colorations?

• 14:04David Grinspoon?

  Yeah, well, the bright stuff seems to be relatively fresh ice, meaning, in the case of this heart, it may be as young as a million years old, which in terms of, you know, planetology is, is like born yesterday. There's no craters on that thing. And so, it's really fresh. The darker stuff is probably ice that has been irradiated and mixed in with organic stuff that, you know, the methane, of course, because it's being irradiated by ultraviolet from the sun, makes organic stuff, like we're made out of, which is one of the cool things about these bodies, is that they all have some organics.

• 14:42Neil deGrasse Tyson?

  So, it's a source of energy for methane to explore other chemical reactions?

• 14:48David Grinspoon?

  Absolutely, yeah. And, and, and the methane is, you know, it is an ice, but it's also a gas at those temperatures. It's probably both on Pluto. And so, you have this weird kind of meteorology where stuff is condensing out and evaporating, depending on the season and the latitude. So, you have stuff moving around on the surface, too, with this process of, of evaporating and condensing.

• 15:08Neil deGrasse Tyson?

  Okay.

• 15:09David Grinspoon?

  Now, you. Places.

• 15:10Neil deGrasse Tyson?

  You guys are a bit audacious, I think, in asserting that Pluto has an atmosphere, when by my notes, it says the atmospheric pressure on Pluto is one one hundred thousandth.

• 15:22Neil deGrasse Tyson?

  The pressure that we have here on Earth.

• 15:24Chuck Nice?

  Wow.

• 15:25Neil deGrasse Tyson?

  You still wanna call it, because the word atmosphere, so let's go there and breathe it. This is the people's first thought. And then you come out and breathe is one one hundred thousandth. So your definition is clearly different from the person in the streets definition.

• 15:37David Grinspoon?

  Yeah, I mean, you know, it depends on what you wanna um call an atmosphere. Uh, you know, maybe you wanna call it a dwarf atmosphere, I don't care. But but it's, you know, it is gas that's gravitationally bound to a planet and interacting with that planet's surface. And there's more of it there than there is out in the vacuum of space.

• 15:56Chuck Nice?

  So so if you were on Pluto and you sneezed, you would actually get rid of the entire planet's atmosphere?

• 16:04David Grinspoon?

  You could probably sneeze some of that stuff right off.

• 16:08Chuck Nice?

  Exactly.

• 16:12David Grinspoon?

  Which is why that astronauts should always, you know, bring some antihistamines when they go to a planet like that.

• 16:17Neil deGrasse Tyson?

  So if it's, is there any kind of life anybody can imagine? Presumably not life as we know it, but life as we don't know it, that could be sustained on Pluto, anywhere on it or within it?

• 16:27David Grinspoon?

  Absolutely, I think the most promising.

• 16:29Neil deGrasse Tyson?

  You would say yes to that?

• 16:31David Grinspoon?

  Yeah, of course, because the thing is, you know, as we're finding with a lot of these icy bodies out there, there's much more activity than we thought there would be, which means there's some kind of energy source. It's internal, uh, probably on Pluto, it's radioactive decay that's that's moving around.

• 16:48Neil deGrasse Tyson?

  Oh, so sources of warmth, okay.

• 16:49David Grinspoon?

  And if you've got sources of warmth on a body that's largely ice, then you figure at some depth within, there's probably liquid water. So we think Pluto probably has an ocean of liquid water at some depth beneath the ice. And there's at least some energy source, and we see organic stuff on the surface, there's probably been some mixing, so.

• 17:10Neil deGrasse Tyson?

  Okay, I think you're you're reaching for it there, I think. But here's one I'll grant you. All right, in five billion years, five billion years, the sun goes red giant. All right, and it engulfs the orbit of Mercury, Venus, and possibly Earth. And that makes it much warmer in the outer solar system. So will that help out your life cause on Pluto?

• 17:30David Grinspoon?

  Definitely, definitely. I mean, you know, as you say, I'm sort of reaching for it for trying to find conditions that might support life today, and that's why I'm thinking about the interior. But yeah, at some point in the future, when the sun continues to heat up as it is doing now and goes, you know, into its late stages and the Earth. Zone of the solar system, what we consider the habitable zone now gets uncomfortably warm. There may be briefly at least a habitable zone in the outer solar system. And yeah, Pluto might actually experience a time where you could even have a liquid water ocean on the surface.

• 18:06Speaker 03

  Wow, so it's like planetary real estate. First rule, buy on the fringe and wait.

• 18:11Neil deGrasse Tyson?

  Right, exactly.

• 18:12David Grinspoon?

  That's right.

• 18:13Neil deGrasse Tyson?

  But also, what did you hear what David said?

• 18:15David Grinspoon?

  The future's in the outer solar system.

• 18:17Neil deGrasse Tyson?

  Did you hear what David said? He said it might get uncomfortably warm here on Earth.

• 18:20Speaker 03

  Yes.

• 18:21Neil deGrasse Tyson?

  We would vaporize. I think that's what you're saying here. So Pluto might be the next frontier to move to when we can no longer live on Earth.

• 18:28Speaker 03

  Right.

• 18:29Neil deGrasse Tyson?

  Or we'll just go to another solar system.

• 18:30David Grinspoon?

  Yeah, but at least it's, you know, moving in the right direction if we go to Pluto, so.

• 18:35Neil deGrasse Tyson?

  So, many new things were discovered about Pluto, and I asked Alan if any of that has changed anything, how we view Pluto? How people should view Pluto based on new information from New Horizons? So let's check out my interview. Other than Pluto's surface, as an object, has it changed anybody's notions of things dynamically? It's a thing orbiting the sun.

• 18:58Speaker 03

  Well, with the exception of Neil Tyson, it's most people that it's a planet.

• 19:02Neil deGrasse Tyson?

  Okay, I'm pummeling him now. I'm giving him a niki on a thing.

• 19:05Speaker 03

  And then when people find out that if you drove around the circumference of Pluto, it's as far as from Manhattan to Moscow, they said, "I didn't know it was that big."

• 19:12Neil deGrasse Tyson?

  Yeah, I would say, whether or not anyone calls it a planet, I think, I learned this word in the Carl Saganian universe, where we get to call it a world. And a world has a certain intimacy to it, a conversational intimacy, because it tells you that it's a place. Maybe we'll go visit it one day. It's interesting to think about and to explore. And maybe that's what matters here, is it a world? The moons of Jupiter are worlds.

• 19:40Speaker 03

  They're planets.

• 19:44Neil deGrasse Tyson?

  Alan Stern has planet on the brain.

• 19:46Speaker 03

  Yeah, well, you know, it's important. My field is called planetary science, so I think it's important that we as practitioners understand what the central objects in our field are. And where Pluto falls in that is secondary to just having a basic, logical, consistent understanding of what are planets.

• 20:03Neil deGrasse Tyson?

  Mm-hmm.

• 20:04Speaker 03

  And there's two ways to go at it. You can go at it scientifically. And scientifically, the physical planet definition says that when objects are big enough to be round by self-gravity.

• 20:14Neil deGrasse Tyson?

  Gravity shapes it.

• 20:15Speaker 03

  And they're not so big that their central temperature causes them to ignite infusion. Anything in between, which is from about a tenth of Pluto's size up to about 10 times Jupiter's mass, will be called a planet. It's very simple. Or you could use the Star Trek test. You know, when the viewfinder comes on, the public knows in about a half a second what they're orbiting. It's a spaceship, it's an asteroid, it's a comet or a planet. Pluto passes by either test, but really, it's really about we as scientists being able to order things into boxes so that we can categorize.

• 20:51Neil deGrasse Tyson?

  So it's our problem.

• 20:52Speaker 03

  In a logical way.

• 20:53Neil deGrasse Tyson?

  It's not Pluto's problem, it's our problem.

• 20:54Speaker 03

  Well, Pluto's an inanimate object.

• 20:57Neil deGrasse Tyson?

  Okay, but of course, whatever is your concern about the legitimacy of the vote, our community voted in 2006 for the new classification. I don't believe...

• 21:08Speaker 03

  Actually, not so. 4% of the International Astronomical Union was there. 4% voted. It was almost 50/50. And so about 2% voted each way, and it went the other way. On a vote made up of non-experts called astronomers, not planetary scientists, I'd like to redo that vote.

• 21:26Neil deGrasse Tyson?

  Okay, so now...

• 21:26Speaker 03

  And really get the experts in it.

• 21:27Neil deGrasse Tyson?

  But fine. What I'm saying is, I don't think anything I did had anything to do with that vote. So, and that's the vote that sets the language. So...

• 21:38Speaker 03

  But seven years ahead of that, running a very prominent exhibit at the American Museum of Natural History.

• 21:43Neil deGrasse Tyson?

  Yeah.

• 21:43Speaker 03

  You wanted to take Pluto and the small planets like it off the list of planets. Didn't you do that?

• 21:50Neil deGrasse Tyson?

  No, not really. No, we never had a list of planets. That's the thing. We never said Pluto wasn't a planet. We just grouped it with Kuiper Belt.

• 21:57Speaker 03

  So if I go over to AMH today, I won't find any numbers like 8?

• 22:01Neil deGrasse Tyson?

  Never. There was never the number 8. I was misunderstood.

• 22:06Speaker 03

  I'm having the best time.

• 22:07Neil deGrasse Tyson?

  The press misunderstood me and my team who did this.

• 22:12Speaker 03

  So Pluto's a planet.

• 22:13Neil deGrasse Tyson?

  So, no, we didn't. The institution did not commit to whether.

• 22:17Speaker 03

  I'm asking Neil.

• 22:19Neil deGrasse Tyson?

  I think.

• 22:20Speaker 03

  That's where you get to make some news, Neil.

• 22:22Neil deGrasse Tyson?

  Let me at least meet you halfway. I think if dwarf planet is a category of planet, I have no problem with that. What happened was people thought the dwarf planet meant is not a planet anymore. And I agree, and that's where I can meet you somewhere.

• 22:37Speaker 03

  Good. So I like that. Dwarf planet is a category planet, just like dwarf stars. The sun is a dwarf star. Would anybody deny it's a star?

• 22:45Neil deGrasse Tyson?

  Yeah, it's a dwarf. Most people don't know it's a dwarf star, but it's a dwarf.

• 22:47Speaker 03

  Yeah, that's pretty good, Neil.

• 22:49Neil deGrasse Tyson?

  Oh, we're shaking hands. Uh-oh.

• 22:51Speaker 03

  On camera. Because Neil just said dwarf planets are planets.

• 22:56Neil deGrasse Tyson?

  We can edit that out. You guys edit that out later.

• 22:59Speaker 03

  You probably will.

• 23:02Neil deGrasse Tyson?

  Guys, I told you to edit that out. Why is it still in there?

• 23:05Chuck Nice?

  Oh, my God. Let me just say, that is a deeply wounded man you're talking to right there. I mean, he is, he just went Taylor Swift on you. We are never getting back together, Neil. Never. It's a planet, damn it. It's a planet.

• 23:21Neil deGrasse Tyson?

  So David, what's your take on all this?

• 23:24David Grinspoon?

  Well, you know, you heard me earlier in this conversation, use the word planet, and that's almost my reflex. Like, I wasn't trying to be provocative or make a point then. It's honestly how I think of it. And I do understand how people that are concerned with thinking about orbits and classification of gravitational influence, you know, might put dwarf planets like Pluto in sort of their own category. But as a planetary scientist, you know, I go to meetings where we talk about planetary geology and processes of planetary atmospheres. And when we're doing that and we're doing comparative planetology, we do use the word planet. Often when we talk about Pluto, we're saying, well, you know, this planet has a crater population that shows that this area is young.

• 24:10David Grinspoon?

  And people don't stand up and go, wait, you know, they correct and go, no, you mean dwarf planet.

• 24:14Chuck Nice?

  That's because they've all been brainwashed.

• 24:15David Grinspoon?

  Maybe.

• 24:17Chuck Nice?

  And can I just put it this way? Would this be fair to say, to look at dwarf planets and bodies such as Pluto, the way the statement would be, all human beings are apes?

• 24:29Neil deGrasse Tyson?

  Not all apes are human beings. So, uh, could it be something along those lines when it comes to dwarf planets?

• 24:35David Grinspoon?

  Well, yeah, I mean, I actually like, I thought the conversation between Neil and Alan that I just listened to was pretty interesting because to me, I mean, I definitely don't have a problem with the reclassification. I think, you know, we've learned enough about these other objects and even about the exoplanets, which they didn't even really get into to, to reexamine the word planet. But I always thought it was a little funny to say, "And a dwarf planet is not a planet." That was the part that seems like sort of an add-on.

• 25:03Neil deGrasse Tyson?

  Like a dig. That was a dig, you're saying? Right. So, so what I did, uh, because of my episode, dealing with the public and Pluto at the museum, I, I published a book called The Pluto Files: The Rise and Fall of America's Favorite Planet. And in there, it's, it's a fact base, and at the end, I save one little section where I have a two-page expression of my opinion. And all I say there, and, and David, you're a sensible guy. I don't see why you would object to this, but I want this on camera to verify once I tell you. Sweet. So, that what we really need, and this echoes a little bit of what Alan was saying. The word planet is not a useful word anymore. When I say planet, I just discovered a planet around another star. Oh, is it rocky? Is it gaseous? Is it near? Is it in an habitable zone? Might it have life? Does it have an atmosphere?

• 25:47Neil deGrasse Tyson?

  You have to ask me 20 questions after I hand you a classification that's, that tells you the word needs improvement. So the classification is far too large. Far too large. And so, we should have 20 different classify, 20 different things. Right. Should be like rocky objects and gaseous objects, objects with rings, objects, and then have, find some words for that. That way I can say I found one of them, and then you're right there.

• 26:12David Grinspoon?

  Absolutely. I mean, we've al, we've always had, um, gas giants and, and terrestrial or rocky earth-like planets.

• 26:19Neil deGrasse Tyson?

  It's already ready to hap, it's ready to happen.

• 26:22David Grinspoon?

  We didn't know that there were more kinds of planets and we're discovering so much in our own solar system and wonderfully around other stars that yeah, I mean, we definitely are evolving the way we think of planets.

• 26:32Neil deGrasse Tyson?

  And I think they should have waited, we should wait until we get a nice, well-defined catalog of exoplanets.

• 26:38David Grinspoon?

  Right.

• 26:38Neil deGrasse Tyson?

  So that when we finally lay down a new set of definitions, it includes not only this solar system, but all others yet to be found.

• 26:45David Grinspoon?

  Nice. Well, I mean, yeah, the definition's going to be reworked and reworked again because we're at our infancy of learning about exoplanets. And you know, the IAU, when they made this-

• 26:54Neil deGrasse Tyson?

  International Astronomical Union.

• 26:55David Grinspoon?

  When they made this vote about Pluto, and I agree, I mean, I think most people agree that that vote wasn't the last word and that it wasn't that well-done. A lot of people that even sort of agree with the decision acknowledged that that was sort of rushed and everything, but also another thing is that they didn't really deal with the exoplanets at all. They were just like, well, we'll wait on that. And so now you have the sort of absurd situation where almost all the planets in the universe, basically all the planets in the universe, are not included in the IAU definition of a planet, in the official definition. So I think there's going to be another stab at it and maybe they'll take another look at this question of whether dwarf planets need to be defined as not planets or simply as another kind of planet.

• 27:36David Grinspoon?

  You know, in a certain sense, I don't really care, you know, it's a little bit distracting. I mean, what's really cool is the fact that we've learned about all these new kinds of objects. I refer to them as planets, I can't help it, but you know, as long as we're talking about them and people are interested in them, then the nomenclature is the most important thing.

• 27:53Neil deGrasse Tyson?

  Well, coming up next, more about Pluto's largest moon, Charon. David, am I pronouncing that right? Charon?

• 28:00David Grinspoon?

  Yes.

• 28:00Neil deGrasse Tyson?

  Good, thank you. And New Horizons continuing journey into the Kuiper Belt when StarTalk returns.

• 28:18Neil deGrasse Tyson?

  Welcome back to StarTalk. I'm here with Chuck Nice.

• 28:21Chuck Nice?

  That's right.

• 28:22Neil deGrasse Tyson?

  And our guest via Skype, planetary scientist David Grin spoon.

• 28:26Chuck Nice?

  Dr. Funky Spoon.

• 28:28Neil deGrasse Tyson?

  That's because that's his handle. That's his Twitter handle Funky Spoon. David, why are you funky?

• 28:33David Grinspoon?

  Well, you know, some of us are just born that way.

• 28:37Chuck Nice?

  Right on.

• 28:38David Grinspoon?

  As you know, I play music too, in addition to.

• 28:42Neil deGrasse Tyson?

  Okay.

• 28:43David Grinspoon?

  So.

• 28:44Neil deGrasse Tyson?

  I will give it to you then. We'll give it to you.

• 28:46David Grinspoon?

  I just can't help it.

• 28:46Neil deGrasse Tyson?

  For now. You're borrowing it. We need more evidence. Well, featuring my interview with Alan Stern, lead investigator of the New Horizons mission to Pluto, NASA's mission to Pluto. And let's talk about their moons. Alright, for the longest while, we didn't even know Pluto had a moon.

• 29:02Chuck Nice?

  But you know what? Here's the thing. Well, before you get to that, because I know you teased that talking about Sharon.

• 29:07Neil deGrasse Tyson?

  Mm hmm.

• 29:07Chuck Nice?

  I need to talk about the fact that I just want to know how you feel about getting hate mail from children for killing Pluto.

• 29:16Neil deGrasse Tyson?

  Oh, oh, yeah, because I got blamed.

• 29:18Chuck Nice?

  I know you got blamed. And you know what's funny? I hate to say this, but Alan almost blamed you in our, in earlier, when we heard in that clip.

• 29:25Neil deGrasse Tyson?

  Uh huh.

• 29:26Chuck Nice?

  It was like, you know, you and your team, Neil.

• 29:28Neil deGrasse Tyson?

  Right.

• 29:28Chuck Nice?

  And it was almost accusatory the way he stopped short of it. He stopped.

• 29:33Neil deGrasse Tyson?

  I have a file cabinet drawer of hate pissed off, angry third graders.

• 29:41Chuck Nice?

  Dear.

• 29:42Neil deGrasse Tyson?

  Whole classes, the teacher organized, organized rebuttals.

• 29:47Chuck Nice?

  Yes.

• 29:47Neil deGrasse Tyson?

  Okay.

• 29:48Chuck Nice?

  Look, I happen to have one right here.

• 29:49Neil deGrasse Tyson?

  Well, you got one?

• 29:50Chuck Nice?

  Yes, I do. Dear Dr. Tyson, you are a big poopy head.

• 29:54Neil deGrasse Tyson?

  I remember that one.

• 29:57Chuck Nice?

  Pluto is my favorite planet. Okay?

• 30:02Neil deGrasse Tyson?

  I was a poopy head in that moment. Yeah, yeah.

• 30:04Chuck Nice?

  So.

• 30:06Neil deGrasse Tyson?

  And yeah, so I was like the leading edge of this. David, I do you, do you, can I get some sympathy or something from you for that?

• 30:14David Grinspoon?

  Well, yeah, of course. Um, you know, I, I was working in, at the Denver Museum when all this came down and I'd have kids, uh, you know, freaking out and wondering what happened to Pluto. I mean, it's very, people get very emotional about.

• 30:26Chuck Nice?

  Why is that? Why is it? I mean, seriously, if you said to me like Venus is our solar system's whore. Nobody would get mad, be like, oh, well, you know.

• 30:36Neil deGrasse Tyson?

  Okay, fine. Yeah, I, I, I, I think it's.

• 30:38Chuck Nice?

  What is it?

• 30:39Neil deGrasse Tyson?

  I think in America, that's why I subtitled my book, The Rise and Fall of America's Favorite Planet.

• 30:44Chuck Nice?

  Right.

• 30:44Neil deGrasse Tyson?

  Because an American discovered it.

• 30:46Chuck Nice?

  Oh.

• 30:47Neil deGrasse Tyson?

  And it was discovered the same year that Walt Disney first sketched the dog that would get the name Pluto.

• 30:53Chuck Nice?

  Uh.

• 30:54Neil deGrasse Tyson?

  So, and, and when you're a little kid, when do you first learn about the solar system in like third or fourth grade? When are you first doing cartoons, you know?

• 31:01Chuck Nice?

  Same time.

• 31:02Neil deGrasse Tyson?

  Around the same time. So.

• 31:03Chuck Nice?

  So the time you learn about the planet, uh, you're learning about the dog or you're, you're admiring.

• 31:07Neil deGrasse Tyson?

  Exactly. So I think Americans had a little extra attachment compared to the rest of the world. I, I asked people in Europe. Uh, in, in France, I said, do you care that Pluto's the quote, the motor? I don't care.

• 31:19Chuck Nice?

  Are you kidding me? Pluto is a peasant planet.

• 31:24David Grinspoon?

  Hey, Chuck, I gotta tell you, it does upset me a little bit when you talk about Venus in that way.

• 31:31Neil deGrasse Tyson?

  Of course it would upset you that way.

• 31:33David Grinspoon?

  I think there's something about it, it being small and kind of an oddball and maybe a little bit of an underdog.

• 31:39Chuck Nice?

  That's it.

• 31:39David Grinspoon?

  People, people were sympathetic with Pluto and it's, it's actually a very interesting phenomenon.

• 31:44Neil deGrasse Tyson?

  Well, plus we would learn that Pluto had, had a moon in 1978. A moon of Pluto was discovered named Sharon.

• 31:51Chuck Nice?

  Sharon!

• 31:52Neil deGrasse Tyson?

  Sharon, which was the name, uh, correct me if I'm wrong, David, the name of the ferry boat driver that would carry your unfortunate soul across the river into Hades. Is that correct?

• 32:04David Grinspoon?

  It, it was also that the, the wife of, of Jim Christie who discovered Sharon, uh, discovered Sharon was, was named Sharon.

• 32:10Neil deGrasse Tyson?

  Oh, nice. Okay.

• 32:11David Grinspoon?

  It was a kind of a twofer there.

• 32:13Neil deGrasse Tyson?

  Okay.

• 32:14David Grinspoon?

  And some people, there's some, some people pronounce it Ca- Charon, but, but, but I, I, Sharon works for me.

• 32:19Neil deGrasse Tyson?

  And also, the, uh, it's not only, uh, Sharon, but it's got four other moons. So Pluto has at least five moons, is that correct?

• 32:27David Grinspoon?

  Yeah, and actually, it has only five moons. I mean, as far as we could tell, one of the things New Horizons did was look really carefully to try to discover other moons, and they actually were very careful because there was this worry that they might hit something. So it was, there was this whole hazard avoidance sense of we really gotta make sure there aren't any other small objects in orbit around Pluto.

• 32:47Neil deGrasse Tyson?

  That would be embarrassing.

• 32:48David Grinspoon?

  Yeah, exactly. Uh, you know, something, something really tiny would, would doom the spacecraft at those speeds. But all they found was this one giant moon Sharon, which we already knew about, and then these, uh, four smaller moons, which are named Nix, Hydra, Kerberos, and Styx.

• 33:05Chuck Nice?

  Wow, you're right. Everything does have to do with death around Pluto.

• 33:09David Grinspoon?

  Yeah, yeah.

• 33:10Neil deGrasse Tyson?

  Well, this was the thematic relevance. All the moons of Jupiter are named of Greek characters in the life of Zeus. Zeus being the Greek counterpart to Jupiter. So we try to be mythologically consistent. Why not? Just as homage to the Greek and Roman history of all of this. So during the flyby, the New Horizons mission also got a good look at Sharon. And so I asked Alan Stern about that. Let's check it out.

• 33:34Speaker 03

  It's 1,200 kilometers, 750 miles across. It orbits pretty close to Pluto. So if you were standing on Pluto, it would be much bigger in the sky than seeing a full moon. And also, it's about as bright as a full moon, because it's icy and very reflective.

• 33:49Neil deGrasse Tyson?

  Oh, because the moon itself is not very reflective.

• 33:52Speaker 03

  Our moon, our moon is kind of just dirt. It doesn't reflect very well, right? But Sharon's icy, and, and we've discovered that it had a really interesting geological pass. It has, um, the largest canyon system.

• 34:04Neil deGrasse Tyson?

  Just to be clear, as bright as a full moon looks to anybody at night, it would be much, much brighter if it were made of ices or something. More reflective than its current substance.

• 34:14Speaker 03

  You mean our moon.

• 34:15Neil deGrasse Tyson?

  Our moon, right, right. I just wanted to make it clear, because people talk about how bright the moon is, or I can read by moonlight, or jog by moonlight, but it would be way brighter if it weren't so dark.

• 34:24Speaker 03

  Exactly.

• 34:24Neil deGrasse Tyson?

  Okay, yeah.

• 34:25Speaker 03

  Yeah, as a matter of fact, so we've learned that Charon has something no other place in the solar system has, it has a dark pole, like an antipole or cap. It has no atmosphere, but it apparently used to in the past, because there's some telltale evidence of that, there's evidence that it used to have an ocean on the inside, like Europa.

• 34:43Neil deGrasse Tyson?

  Whoa, because Europa has a subsurface ocean.

• 34:45Speaker 03

  Yeah, right. We found that the inside has ammonia ice in it, and we see that in the ejecta blankets of craters, where we can tell the composition of what came out of the center.

• 34:55Neil deGrasse Tyson?

  Ooh, so there's a term for that. I never knew it had a term. So, an asteroid or some impactor strikes, and it makes a hole deep enough that whatever's below the crater range splashes up.

• 35:06Speaker 03

  It excavates.

• 35:07Neil deGrasse Tyson?

  Excavates that material.

• 35:08Speaker 03

  And Charon's got this enormous canyon system, the dwarfs, the Grand Canyon. It's just another cool place.

• 35:15Neil deGrasse Tyson?

  I think we need to rename our Grand Canyon.

• 35:17Speaker 03

  Yeah.

• 35:18Neil deGrasse Tyson?

  Because now that we've got, there's the Mars, you know, everybody's got a canyon bigger than Earth.

• 35:23Speaker 03

  What do you think?

• 35:23Neil deGrasse Tyson?

  We gotta, we gotta rename this.

• 35:25Speaker 03

  Even Pluto and Charon, yeah.

• 35:28Neil deGrasse Tyson?

  So David, you got a name for our Grand Canyon? The not-so-Grand Canyon? Baby Grand Canyon. Baby Grand, the Baby Grand. The Baby Grand Canyon. Steinway Baby Grand Canyon. We'll have it sponsored.

• 35:39David Grinspoon?

  Somewhat impressive canyon.

• 35:41Neil deGrasse Tyson?

  So David, what else can you add about Charon?

• 35:43David Grinspoon?

  Well, Charon is another delight, you know, even on its own, it was, it was almost worth the, the price of admission of getting there. It's got some strange features. For one thing, it has this northern cap that's significantly darker than the rest of, of the moon.

• 35:58Neil deGrasse Tyson?

  Yes, it's kind of an anti-ice cap, right?

• 36:00David Grinspoon?

  Yeah, yeah, exactly. And, and there's some suspicion that it might have to do with exchanging gas between Pluto and Charon, if not at present, maybe in the past.

• 36:12Neil deGrasse Tyson?

  No, no, that system, that system is tipped, right? That orbital system is tipped relative to Pluto's plane of orbit around the sun, is that correct?

• 36:20David Grinspoon?

  Yeah, exactly. And uh, but it's, of course, it's tidally locked now. So it just, if you were on Charon, there'd be one s- eh, one place on Charon where Pluto would always be overhead and you could just stay there and, and, and go around and watch, watch Pluto go by.

• 36:35Neil deGrasse Tyson?

  In other words, Charon does not rotate relative to Pluto.

• 36:38David Grinspoon?

  Yeah.

• 36:38Neil deGrasse Tyson?

  Yeah. It always fe- shows the same face.

• 36:40David Grinspoon?

  Yeah.

• 36:41Neil deGrasse Tyson?

  Mm-hmm.

• 36:41David Grinspoon?

  Yeah.

• 36:42Chuck Nice?

  Wow, that's pretty cool.

• 36:43Neil deGrasse Tyson?

  It's, it's very cool. So it's double tidal lock.

• 36:45Chuck Nice?

  Double t- yeah.

• 36:45Neil deGrasse Tyson?

  Did I tell you? Did I tell you in high school?

• 36:47Chuck Nice?

  No.

• 36:48Neil deGrasse Tyson?

  I didn't tell you?

• 36:48Chuck Nice?

  No.

• 36:49Neil deGrasse Tyson?

  I didn't tell you?

• 36:49Chuck Nice?

  No.

• 36:49Neil deGrasse Tyson?

  Okay. In high school, I used, I wrestled in high school.

• 36:52Chuck Nice?

  Well, that I knew.

• 36:53Neil deGrasse Tyson?

  Uh, I was undefeated and I was captain.

• 36:55Chuck Nice?

  Okay.

• 36:55Neil deGrasse Tyson?

  I was kicking some serious ass and I wanted to invent a new wrestling move called the double tidal lock.

• 37:02Neil deGrasse Tyson?

  Doesn't it sound like a move that has to have that name?

• 37:04Chuck Nice?

  Right.

• 37:04Neil deGrasse Tyson?

  Okay. So, but I never perfected it, but I, I'll show it to you later.

• 37:07Chuck Nice?

  We gotta get, no, don't show me.

• 37:12Neil deGrasse Tyson?

  So David, tell me about moons. Our moon, people talk, they've been talking for a long time about moons being important to develop life on a planetary surface. Why? I've never really agreed with that connection. Maybe you can bring me on board.

• 37:25David Grinspoon?

  I agree with it either, uh, strictly, but the logic is that, uh, on Earth, our giant moon, and by the way, Earth and Pluto have in common that they have the two giant moons in the solar system as far as the relative size of the moon to the planet. You know, Earth's is rather extreme. Pluto's is even more extreme as a, it being a fraction, a sizable fraction of the, the planet.

• 37:48Neil deGrasse Tyson?

  Yeah, in fact, for Pluto and Charon, the middle point of their gravity is outside of the physical body of Pluto, right?

• 37:54David Grinspoon?

  So it's a double planet.

• 37:56Neil deGrasse Tyson?

  It's basically a double planet.

• 37:57David Grinspoon?

  Whatever.

• 37:57Neil deGrasse Tyson?

  Damn, he got me to say planet.

• 38:01Chuck Nice?

  I was just about to say. You just said planet.

• 38:05Neil deGrasse Tyson?

  This is diabolical plot.

• 38:07David Grinspoon?

  On Earth is that the moon stabilizes Earth's climate by acting almost as like the outrigger on a canoe by preventing the, the, uh, axis of Earth from wobbling more. And it, it certainly has played that role. Now, whether you could say without the moon, Earth would be lifeless, or would just have life that had adapted to, uh, somewhat more wobbly climate, I'm not sure, but that, that is the idea.

• 38:30Chuck Nice?

  That so the moon, our moon acts as a keel, kind of.

• 38:34Neil deGrasse Tyson?

  In a way, yeah.

• 38:35Chuck Nice?

  That's amazing.

• 38:36Neil deGrasse Tyson?

  That's exactly right. And so.

• 38:38David Grinspoon?

  Gravitational keel.

• 38:39Chuck Nice?

  A gravitational keel.

• 38:40Neil deGrasse Tyson?

  I would say, look at the temperature range over which we survive or even thrive anyway.

• 38:45Chuck Nice?

  Right.

• 38:45Neil deGrasse Tyson?

  On Earth. We have humans living at the equator.

• 38:47Chuck Nice?

  True.

• 38:48Neil deGrasse Tyson?

  And Eskimos live in the Arctic.

• 38:49Chuck Nice?

  The Arctic.

• 38:50Neil deGrasse Tyson?

  So, so I'm, I don't think that would, we would fear that.

• 38:53David Grinspoon?

  Yeah, I agree with you. I mean, you can imagine somebody looking at our planet from some other kind of planet and go, oh, look at these seasons. They have winter and summer. Nobody could possibly live there.

• 39:04David Grinspoon?

  It may just be that kind of Arctic.

• 39:05Neil deGrasse Tyson?

  Okay, cool. So New Horizons went by Pluto and it kept going on a flyby and is looking for other stuff out there in the Kuiper Belt. I had to ask Alan Stern, what's next for New Horizons? Check it out.

• 39:17Speaker 03

  So back in November, October, November, we fired the engines a series of times to target it for its next flyby. It's about a billion miles past Pluto. It's a building block of these small planets like Pluto and Eris and the others. It's about the size of Chesapeake Bay. It's four billion years old. It's always been in the deep freeze. So it's scientifically a great sample of that early era.

• 39:38Neil deGrasse Tyson?

  Okay.

• 39:38Speaker 03

  Um, it doesn't have a really good name yet. The, it has a license plate. It was detected by the Hubble for New Horizons. It's called 2014, which is the year it was found. MU69, which is a jawbreaker.

• 39:49Neil deGrasse Tyson?

  Okay.

• 39:50Speaker 03

  So we'll do better. We're gonna have a naming contest with NASA and pick something.

• 39:54Neil deGrasse Tyson?

  Good. So that's gonna be another flyby.

• 39:57Speaker 03

  That'll be a flyby.

• 39:58Neil deGrasse Tyson?

  All right.

• 39:58Speaker 03

  And we know when. It's a very easy date to remember. It's January 1st, New Year's Day, 2019.

• 40:04Neil deGrasse Tyson?

  2019, okay. I'll put that on my calendar. And again, you're flying by. Do you have fuel for yet a third destination?

• 40:10Speaker 03

  Probably not, but we have plenty of fuel to run the spacecraft on a Voyager-like mission way out to the Helium.

• 40:17Neil deGrasse Tyson?

  Oh, okay.

• 40:18Speaker 03

  Yeah.

• 40:18Neil deGrasse Tyson?

  Cause that uses less energy, of course.

• 40:20Speaker 03

  Yeah, yeah, yeah.

• 40:21Neil deGrasse Tyson?

  And of course you've got, this is the fastest spacecraft ever launched from Earth.

• 40:25Speaker 03

  It is.

• 40:26Neil deGrasse Tyson?

  And you will leave the solar system the way Voyager did.

• 40:28Speaker 03

  Exactly.

• 40:28Neil deGrasse Tyson?

  Okay. Will you ever overtake Voyager?

• 40:30Speaker 03

  No.

• 40:31Neil deGrasse Tyson?

  Oh, that's too bad.

• 40:31Speaker 03

  And you're and a lot of people wonder why if it was the fastest launch, how was Voyager ahead and staying?

• 40:36Neil deGrasse Tyson?

  I think because Voyager cheated. It got some extra boost from Jupiter, I bet.

• 40:39Speaker 03

  It got four boosts, one from each giant planet.

• 40:41Neil deGrasse Tyson?

  Oh, my God. I didn't know it was all four.

• 40:43Speaker 03

  Yeah.

• 40:43Neil deGrasse Tyson?

  Oh, my God.

• 40:43Speaker 03

  And we only got Jupiter. So they they're a little faster than us.

• 40:46Neil deGrasse Tyson?

  Okay.

• 40:47Speaker 03

  But that's fine.

• 40:48Neil deGrasse Tyson?

  Okay, so this is stealing some of the orbital energy of a

• 40:51Speaker 03

  Of a giant planet.

• 40:52Neil deGrasse Tyson?

  Of a giant planet, and you get a little boost out of that.

• 40:54Speaker 03

  Yeah.

• 40:55Neil deGrasse Tyson?

  Okay, that's fine. I don't think the planets mind.

• 40:57Speaker 03

  I don't think they notice. They're inanimate objects.

• 41:02Neil deGrasse Tyson?

  So David, tell me something about the Kuiper Belt. Is it it's real enough and it extends out there?

• 41:08David Grinspoon?

  It's I mean, the Kuiper Belt is is this vast outer realm of our solar system that we really didn't even start to learn about until, um, you know, the nineteen eighties and nineteen nineties and

• 41:20Neil deGrasse Tyson?

  By the way, it's it's not a coincidence. It's not simply a coincidence that that's around the time where people are wondering whether Pluto just belongs in the Kuiper Belt as as a as a species of object, right?

• 41:31David Grinspoon?

  Absolutely. No, that was the discovery that led to this whole question of reclassification.

• 41:36Neil deGrasse Tyson?

  Right.

• 41:37David Grinspoon?

  Was the fact that there are lots of objects out there, not just Pluto, and that led some people say, oh,

• 41:42Neil deGrasse Tyson?

  How many is lots? How many is lots?

• 41:45David Grinspoon?

  Oh, gosh, it's it's, um,

• 41:47Neil deGrasse Tyson?

  By the way, when you're funky, you can't use the word gosh. Just those two.

• 41:52David Grinspoon?

  Well, damn.

• 41:53Speaker 03

  There you go. That's funky.

• 41:55Neil deGrasse Tyson?

  Gosh, Darnley. Golly, golly gee.

• 41:58Speaker 03

  Didly doo.

• 42:01Neil deGrasse Tyson?

  I'll tell you, only barring that funky moniker, you gotta keep earning it, but go on.

• 42:06David Grinspoon?

  There there are millions of objects in the Kuiper Belt, you know, it's because you get to smaller and smaller objects and there are, you know, just little chips of things, too, because it's been collisional in the past. So it's it's vast.

• 42:19Neil deGrasse Tyson?

  And you call them objects, but what we can call them comets. They're they're icy, right?

• 42:23David Grinspoon?

  Yeah, well, I mean, exactly. I mean, if if you took them into the inner solar system, a lot of them would turn into comets. They'd start to develop tails and evaporate material.

• 42:32Neil deGrasse Tyson?

  Like Pluto would do? Yeah, go on.

• 42:34David Grinspoon?

  And, you know, the larger ones are, as we've been discussing, dwarf planets, the larger ones around because of self-gravity. So there's a whole spectrum of objects. You know, it's it's a vast realm. It's, in a lot of ways, it's the largest part, the main part of our solar system in terms of number of objects and in terms of the volume of space it takes up. And it is a belt, by the way. It's not a sphere of comets like we have farther out in the solar system. It's it's concentrated along that plane where the planets all.

• 43:05Neil deGrasse Tyson?

  So you have the Oort Cloud, which is an icy body of comets, a zone of comets which is spherical, so we call it a cloud. And this is a belt, like the asteroid belt, which is kind of slightly flattened in a plane. So this is the lingo. Yeah, okay.

• 43:20David Grinspoon?

  Yeah, I mean, it's it's a thick, thickened belt. You know, the objects are kind of, they're not all neatly in that plane. They're all a little bit tilted so that it's a it's a fat belt, but it's not, they're not isotropic. That is, they're not equally in all directions. They are concentrated in the plane that the planets orbit.

• 43:37Neil deGrasse Tyson?

  So this will go on for another, how much power does the thing have to keep going?

• 43:42David Grinspoon?

  It's supposed to, you know, in terms of, it's it's got a plutonium power source. And, um.

• 43:48Neil deGrasse Tyson?

  Quaint. Very nice. It's plutonium.

• 43:50Chuck Nice?

  Plutonium.

• 43:51Neil deGrasse Tyson?

  Yeah.

• 43:53David Grinspoon?

  We sent plutonium past Pluto.

• 43:54Neil deGrasse Tyson?

  Yeah, yeah, not uranium. That'd be a Uranus thing.

• 43:58David Grinspoon?

  It's gonna slowly lose power, but it's gonna last for decades, probably at least until the 2040s. Um, they should be able to stay in contact with it, just as we've been able to stay in contact with the Voyagers for decades after they completed their primary mission.

• 44:13Neil deGrasse Tyson?

  And just if I remember correctly, you cut your teeth on Voyager, didn't you, back in the 70s and 80s?

• 44:18David Grinspoon?

  Yeah, I was a student, an undergraduate intern at the Voyager Jupiter encounter in

• 44:24Neil deGrasse Tyson?

  Cool.

• 44:24David Grinspoon?

  1979. It was a really life-changing and mind-blowing experience.

• 44:29Chuck Nice?

  Wow, we have so much in common. I watched every episode of Star Trek Voyager.

• 44:38Neil deGrasse Tyson?

  And you would have had, would that might have been your first encounters with Carl Sagan at the time? Who was actively Voyager?

• 44:43David Grinspoon?

  Yeah, Sagan was a mentor of mine then, and just getting to, getting to see him work and interact with the rest of the team. And of course, they were filming Cosmos, the older Cosmos. And, you know, so there were like film crews in there while they were looking at the first pictures from Jupiter. And, you know, as a, as a wide-eyed undergraduate kid, you know, that was a pretty mind-blowing experience.

• 45:05Neil deGrasse Tyson?

  Nice. Well, when we come back, we're gonna talk about Planet Nine.

• 45:10David Grinspoon?

  Hmm.

• 45:11Neil deGrasse Tyson?

  What is that?

• 45:12David Grinspoon?

  Ooh.

• 45:13Neil deGrasse Tyson?

  Ooh, it's a hypothetical planet could be hiding in the farthest reaches of the solar system. When StarTalk continues.

• 45:36Neil deGrasse Tyson?

  We're back on StarTalk with my co-host, Chuck Nice. That's right. And our guest, in via video call, David Grinspoon, planetary scientist. David, good to have you, as always. Thanks, always fun to be here. We're featuring my interview with Alan Stern, who's the PI for the New Horizons mission, the NASA mission to Pluto and beyond. Yes. And now, earlier this year, since, David, we got you online and you were outer, outer solar system guy. Earlier this year, two Caltech astronomers asserted the existence of a Planet Nine deep in our solar system. Mass maybe about 10 times that of Earth. So none of this little puny pipsqueak stuff. Right, we don't have to worry about whether or not this is a planet. Exactly, exactly.

• 46:20Neil deGrasse Tyson?

  Size does matter. And I think the numbers they put out were like 20 times farther from the Sun, on average, than Neptune. And it might take 10 or 20,000 years for it to complete one orbit. Wow. Around the Sun. So I had to ask Alan, because he's... It's a long day, man. It's a long year. It's a long year. Oh, that's a year, sorry, not, not, yeah. Phil. Yeah, one revolution. It would never turn one. Yeah, never turn one. If you're human. So I asked Alan Stern about this Planet Nine. Let's find out.

• 46:53Neil deGrasse Tyson?

  Tell me about Planet 9.

• 46:55Speaker 03

  A Pluto?

• 46:59Neil deGrasse Tyson?

  I'm pummeling him again, let the record show.

• 47:01Speaker 03

  I was widely quoted, you know, actually, I think it was Nadia Drake that did the article that asked me about that designation, you know, which I really think.

• 47:10Neil deGrasse Tyson?

  See, that's a beef between you and Mike Brown.

• 47:12Speaker 03

  I think.

• 47:13Neil deGrasse Tyson?

  Mike Brown named it Planet 9.

• 47:14Speaker 03

  Yeah, and I think that was disrespectful of Clyde Tombaugh and his living relatives and the legacy of what he did. So I was widely quoted as saying, apparently Caltech professors can't count. That became a hashtag, Caltech can't count.

• 47:29Neil deGrasse Tyson?

  I missed this, was this in a Twitter war?

• 47:31Speaker 03

  Just a couple of weeks ago. Yeah, it was a Twitter war, but we had a good time. But you know, if you actually count all the objects that are small planets in the solar system, it's actually up around 23.

• 47:42Neil deGrasse Tyson?

  Yeah, it's a couple of dozen. And so, yeah, he probably should have, there are many more creative things he could have called it as a placeholder name. He could have easily just called it Planet X, and that would have been perfectly fine. It would have been even cool. And it's mysterious.

• 47:55Speaker 03

  The X-Files.

• 47:56Neil deGrasse Tyson?

  Yeah, yeah, yeah, yeah, okay. And so, can you comment on how Planet 9 was discovered? Should we have as much confidence as Mike Brown did in the method?

• 48:11Speaker 03

  Are you talking about Pluto again?

• 48:13Neil deGrasse Tyson?

  No, I'm talking about Planet 9.

• 48:16Speaker 03

  We're not gonna call it that, not today.

• 48:18Neil deGrasse Tyson?

  He's not gonna call it.

• 48:19Speaker 03

  No.

• 48:20Neil deGrasse Tyson?

  Okay, Planet X.

• 48:21Speaker 03

  What would you like to call it?

• 48:22Neil deGrasse Tyson?

  Planet X. The object Mike Brown called Planet 9, which I'm happy to call Planet X.

• 48:26Speaker 03

  Thank you.

• 48:27Neil deGrasse Tyson?

  Okay, could you comment on the method of how that was?

• 48:29Speaker 03

  So it hasn't been discovered.

• 48:31Neil deGrasse Tyson?

  Not directly, right.

• 48:32Speaker 03

  And there have been many claims in my career of, we think we can predict the planet. A lot of them fall apart. In fact, even the claim that led to the discovery of Pluto was, they did the math wrong, and Pluto was found only through Clyde Tombaugh's hard work.

• 48:48Neil deGrasse Tyson?

  So David, I looked at the research paper that made this announcement. It seemed pretty legit to me using sort of gravitational

• 48:58Neil deGrasse Tyson?

  Calculations. Thank you. No worries. That's what I'm here for.

• 49:03Neil deGrasse Tyson?

  So you do the inverse calculation for the gravity equations. Normally you say, here is the mass. What is the force of gravity at some point? Right. But instead, what you say is, there, things are behaving in a way that is surely the result of some source of gravity we don't know anything about. Let's look at how they're behaving and infer the existence of a source of gravity elsewhere in space. Gotcha. Basically what they did, David, correct?

• 49:29David Grinspoon?

  Yeah, yeah. I mean, I think it's a good piece of work and it's definitely legit. Whether or not their specific prediction will pan out, who knows? I mean, as Alan said in your discussion with him, there's a history of this kind of prediction being off. It's a hard thing to do. But certainly they saw a pattern in the orbits of other objects that seems to be non-random and seems to imply the existence of some other mass. And, you know, what's great about science is they made a prediction. We'll look, either the object will be there or it won't be and science will move along. But I think as Alan said also, you know, there are bound to be a lot of objects out there. We are going to find other planets in our solar system.

• 50:06Neil deGrasse Tyson?

  Where did they come from?

• 50:09David Grinspoon?

  Well, you know, the origin of the solar system was messy. There was shuffling around of the giant planets and a lot of pretty sizable objects got tossed out. That's why we have a Kuiper Belt, for instance. There was this tossing out of planetesimals of the little planets and some not-so-little ones got shuffled around as well.

• 50:28Neil deGrasse Tyson?

  Wait, just quickly, so you're telling me the Kuiper Belt was not left over from the origin of the solar system? You're saying it may be the castaway debris from what was going on from within the, with the inner solar system?

• 50:40David Grinspoon?

  Yeah, I mean, well, it's it's left over in the sense that it's a remnant of that process. But that process was one of shuffling around and tossing things out of the inner solar system and ending up elsewhere. There was a lot of chaotic.

• 50:52Chuck Nice?

  It's our inner solar system junkyard, basically.

• 50:55Neil deGrasse Tyson?

  That's what you're saying.

• 50:56Chuck Nice?

  It's our inner solar system junkyard.

• 50:58Neil deGrasse Tyson?

  So it might have, so there's some cast, some, what you're saying is there are much larger castaways out there, if this prediction is correct. It might not be the only one, because this, we only happen to infer its presence because it has a visible effect on other Kuiper belt objects. But there could be many large planets out there, is what you're suggesting.

• 51:16David Grinspoon?

  Yeah, I, I think there, there, there should be, based on what seem to be the best theories we have of solar system formation. And it may be that, you know, this specific prediction, even if it's wrong, will lead us to other things. We, I think we will find more planets.

• 51:30Neil deGrasse Tyson?

  So is this gonna give you, is this gonna give us another source of predicting mass extinctions on Earth? That this thing only comes around every 10 or 20,000 years? That'll disrupt Kuiper belt comets and send them raining down on Earth?

• 51:42David Grinspoon?

  Well, it could. I mean, you're referring to, you know, there was this idea of Nemesis, um, was like, yeah, basically a companion to the sun, which every once in a while would disturb the outer cloud of comets and send objects in. The problem with that is that, I, I think the evidence that there's a periodic signal, that, that, that extinctions come in regular intervals, isn't really very good. And so it may be explaining something that doesn't really need an explanation, you know, so I'm, I'm kind of skeptical of that, just because I don't see the, the signal in the, in the data of Earth.

• 52:15Neil deGrasse Tyson?

  So it turns out, in addition to Planet 9, Alan Stern told me Planet 9 could just be, excuse me, Planet X.

• 52:23Chuck Nice?

  Planet X, right.

• 52:24Neil deGrasse Tyson?

  Could just be the tip of an iceberg of many, many larger planets in the outer solar system. Let's check it out.

• 52:32Speaker 03

  Modern planetary science is pretty sure that as we can look further and further with better and better technology, we will find more planets further out and lots of them, and even big ones, and I-

• 52:43Neil deGrasse Tyson?

  Big ones like Neptune sized, like-

• 52:45Speaker 03

  Certainly Earth sized.

• 52:46Neil deGrasse Tyson?

  Yeah.

• 52:47Speaker 03

  The models suggest that Earth sized planets in the Oort Cloud are a good bet.

• 52:50Neil deGrasse Tyson?

  Mm-hmm, mm-hmm. So, we should watch that space?

• 52:53Speaker 03

  Yeah, we absolutely should. It'll be exciting.

• 52:55Neil deGrasse Tyson?

  Yeah, yeah.

• 52:56Speaker 03

  But we're gonna have to get used to the number that there are just large numbers of planets, just like there are large numbers of stars.

• 53:01Neil deGrasse Tyson?

  Mm-hmm.

• 53:02Speaker 03

  And who knew in the 20th century that the solar system was so good at making so many planets?

• 53:07Neil deGrasse Tyson?

  And are some of these planets, do we think, escaped from the inner solar system? And they're just sort of wandering out there?

• 53:12Speaker 03

  Well, a lot of the ones that are in the Oort Cloud came from the middle solar system, the region of the giant planets. When the giant planets got big, their gravity was enough to clear out all kinds of stuff, littler stuff. It threw the comets to the Oort Cloud, it threw a lot of comets out of the solar system altogether, it threw planetesimals, which are 10,000 times bigger than comets, it flung small planets around, and even big planets, because Jupiter can haul an Earth all the way to the Oort Cloud.

• 53:40Neil deGrasse Tyson?

  I didn't know that. Oh, yeah. Why not? I mean, it's Jupiter-

• 53:44Speaker 03

  In fact, there's a theory that some dynamists work on that indicates that even a Neptune or Uranus may have been ejected. There may have been a fifth giant planet in our solar system. And so, some of those things got thrown completely out into interstellar space, and some got stuck on the very edge of the solar system, the lip of the potential well, called the Oort Cloud, and it's kind of the solar system's attic.

• 54:03Neil deGrasse Tyson?

  So, once again-

• 54:04Speaker 03

  You know, everything got thrown up there, and we're gonna go find it when our-

• 54:07Neil deGrasse Tyson?

  So, the more we learn about them, the more nuanced and the more complex it is. And that's a good thing.

• 54:11Speaker 03

  Yeah, I think so.

• 54:14Neil deGrasse Tyson?

  David, give me some final reflections on all of this.

• 54:18David Grinspoon?

  Well, the Oort Cloud is a magnificent structure. You know, we think of the stars as so far away and our solar system is isolated, but if you include the Oort Cloud around our star, and those probably around others, then they're almost touching. I mean, the Oort Cloud goes maybe a third of the way to the nearest star. It's, you know, it's something like a light year in diameter.

• 54:37Neil deGrasse Tyson?

  And just to clarify, we're not speaking of a gaseous cloud here. We're speaking of a- Volume populated by a swarm, I love that word, a swarm of icy bodies.

• 54:47Chuck Nice?

  Right.

• 54:47Neil deGrasse Tyson?

  That from a distance it looks like a, like when you say a cloud of bees.

• 54:50Chuck Nice?

  Right.

• 54:51Neil deGrasse Tyson?

  Same kind of thing.

• 54:51Chuck Nice?

  Same deal.

• 54:52David Grinspoon?

  Yeah, and it's an isotropic sphere, meaning that it's not flat like everything else in the solar system. It's completely round. There's many comets in any direction you can point from the sun. And it's the sort of reservoir of icy stuff that once in a while, something gets disturbed by a passing star or one of these planet X's or whatever, and comes flying in towards the sun. And that's when we see it develop a big tail.

• 55:16Neil deGrasse Tyson?

  So it's cool. I think when, if a comet comes in from above the solar system, we know it's going to be an Oort Cloud comet, because that's the only thing that actually has comets that can come from that direction.

• 55:24Chuck Nice?

  That's right.

• 55:25Neil deGrasse Tyson?

  Right, right. So Chuck, what do you, how do you, what do you make of all this?

• 55:29Chuck Nice?

  Well, you know, I think that it's very clear that people are passionate about planets, which I think is a good thing. And I just love that there are scientists having Twitter wars like Donald Trump. I think that is awesome.

• 55:45Neil deGrasse Tyson?

  So Twitter wars over things other than Donald Trump's hair?

• 55:48Chuck Nice?

  Exactly. Yeah, I think that's great.

• 55:50Neil deGrasse Tyson?

  What I like about it is the, the idea, which is an emergent discovery, David, correct? That many things that we identified as planets in stable orbits around host stars could have been flung from those host stars and could just be wandering interstellar space.

• 56:09David Grinspoon?

  Absolutely. And when Alan, when Alan mentioned a Neptune getting thrown out of our solar system, I couldn't help but thinking, well, does that mean that one of these days a Neptune's going to come flying into our solar system?

• 56:19Neil deGrasse Tyson?

  Yeah, it'll be a flyby, you know, it's like, what are you doing in my neighborhood?

• 56:23Chuck Nice?

  Right.

• 56:23Neil deGrasse Tyson?

  I thought I told you never to come around here.

• 56:25David Grinspoon?

  See what's going to happen if a Neptune comes flying.

• 56:27Neil deGrasse Tyson?

  But what would be cool is if some of those planets still had a residual heat source, such as Earth still does.

• 56:34Chuck Nice?

  Right.

• 56:34Neil deGrasse Tyson?

  And if that's the case, you could have life possibly evolving on planets.

• 56:40Chuck Nice?

  On a totally rogue planet.

• 56:41Neil deGrasse Tyson?

  On a totally rogue planet.

• 56:43Chuck Nice?

  Right.

• 56:43Neil deGrasse Tyson?

  And they will know nothing of a host star as they wander through space.

• 56:48David Grinspoon?

  We don't need no stars.

• 56:49Neil deGrasse Tyson?

  We don't need no stinking.

• 56:50Chuck Nice?

  Don't need no stinking stars.

• 56:52Neil deGrasse Tyson?

  David Funky Spoon, David Grin Spoon, thanks for being on StarTalk. And again, welcome to the community of StarTalk All-Stars. I look forward to seeing you in many ways and times.

• 57:04David Grinspoon?

  Thanks a lot, Neil.

• 57:05Neil deGrasse Tyson?

  And Chuck.

• 57:06Chuck Nice?

  Yes.

• 57:06Neil deGrasse Tyson?

  Always good to have you, man.

• 57:07Chuck Nice?

  Always good to be here.

• 57:08Neil deGrasse Tyson?

  This has been our show. Thanks for tuning in to StarTalk, featuring my interview with Alan Stern. And as always, I am Neil deGrasse Tyson bidding you to keep looking up.