StarTalk Radio - Unveiling Pluto, with Alan Stern and Neil deGrasse Tyson

Episode Date: July 15, 2016

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. Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

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

Looking good. Got your NASA uniform on. That is correct, sir. I am wearing a NASA shirt. NASA t-shirt. Very good. Trying to get good with me. You don't need to do that. I love you no matter what. I appreciate it, man. I really do. Actually, when I cover, I'm wearing a shirt over top of this shirt, and I have to make sure that the M stays visible. Otherwise, it looks like assa.

Okay, fine. Which, for some reason, makes sense when I wear it. Today, we're talking about Pluto and the farthest reaches of our solar system. Yeah. A lot of stuff out there. Featuring my interview with Mr. Pluto himself, Alan Stern. Yes. He's a friend and colleague.

He's the principal investigator, the PI, of NASA's New Horizons mission to Pluto. That's right. He's also a planetary scientist at the Southwest Research Institute in Boulder, Colorado. It's no Hayden Planetarium, I'll tell you that. No, stop it. Just saying. Actually, Boulder, Colorado, they have the real sky. Yeah, they do.

They don't know no noise pollution there, no light do. No noise pollution there. No light pollution. Exactly. No light pollution. 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. And it was awesome. Who's also an expert on the solar system. And it was great. We're going to bring in planetary scientist David Grinspoon.

David, where are you? Hey there. Oh, hey, dude! Your Twitter handle is Dr. Funky Spoon, which every time I hear it, I gotta recite it. Funky Spoon! Dr. Funky Spoon! You're a senior scientist at the Planetary Science Institute, and where's that? Well, Planetary Science Institute is in Tucson, but I'm actually in Washington, DC. We're sort of a distributed beast, the Planetary Science Institute. We have members all over the world, and I'm here. I'm part of the Washington

Outpost. 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 correctly. I think I own that book. What was that one called? 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 mystery. You said Venus Revealed. It might have been a better title, Venus Unveiled. Yeah, yeah. Then you get the double thing. Duvalantandra going on there there seeing as how Venus, the Milo and you know maybe the next edition I'll go for the unveiling

and also you care about Pluto and I'm told you're working on a new book with Alan Stern what's that one called? yeah boy I love Pluto and Alan and I are working on a book called Chasing New Horizons okay

little word play there, New Horizons. Okay. Okay. A little word play there. New Horizons, the mission, and right? Chasing New Horizons. When does that come out? It comes out next year, 2017. Nice. Okay.

We'll look forward to that. And by the way, you are one of our newly knighted StarTalk All-Stars. I'm saying congratulations, but it's up for you to say whether you want to be that or not. Oh, I very much want to be. I'm really excited to be a StarTalk All-Star. I had a blast at our launch party and recording the first few episodes. I'm looking forward to doing more. Excellent.

And this is not your first time on the air with us, so it's great having you. So tell me about New Horizons. It already passed by Pluto, right? When did that happen? Yeah, it happened just about a year ago, or approaching a year ago, on July 14th, 2015. Okay. It was a long time coming. So, 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 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. Like George Bush over Katrina. Yeah, right. We're doing a heck of a job. I mean, 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 we were lucky to be able to do a flyby. We had to launch a really fast rocket, throw everything we had at it basically just to get a very small spacecraft there. And even so, it took how long? Even so? It took nine years. Nine years. Now, I've tried to spread this fact far and wide that the first rule of any science experiment

is that it needs to be completed before you die. So is that fair enough, David? Is that a fair enough first rule? Well, I think it's a good rule. It's going to be challenging for some of the things we would like to do in the future, like getting to the exoplanets, unless we greatly extend our life expectancy. But yeah, I tend to favor projects that I might have some chance of seeing to completion. 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? Yeah, and then we also had to do a Jupiter flyby to further accelerate. Amazingly, New Horizons took one year to get to Jupiter. I mean, think of how fast that is. 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. Just to be clear, you stole some of Jupiter's orbital energy and gave it to New Horizons. Just confess that.

We pilfered a little bit of momentum from Jupiter. I don't think Jupiter's going to care, but it really helped us out a lot. So we'll get back to that in a minute. But just some facts about Pluto, named for the god of the underworld, right? That's right. And all this time I thought it was the dog. I can't believe that. 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. I vote for death. Death is so much cooler. It's way cooler. Yeah, but an entire planet just devoted to death? I don't know.

Hey, listen, it worked for Darth Vader. Wait, 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, just kind of reminds you. By the way, just, what is the mass of Pluto relative to Earth's moon?

Pluto is really, really tiny for a planet or for an object that some people might call a planet. And it is, in fact, only about a sixth the mass of Earth's moon. Okay. So it's really, you know. Okay, so just fess that up. I know what you're saying, man. Listen, even a micropenis is a penis. Time to throw to the clip.

Wait, I thought that was called a dwarf. Oh, never mind. So Alan Stern came to town, and I sat down with him to catch up on New Horizons, fly by of Pluto. Let's check it out. What a year it was for New Horizons. Oh, my gosh. I just want to say congratulations.

My gosh. Oh, thanks a lot. You know, New Horizons is a huge team of people. Actually, over 2,500 people worked to build it. Oh, my gosh. And what center, what institutions were? It's a joint project funded by NASA, but a joint project of the Southwest Research Institute and the Johns Hopkins Applied Physics Lab. Lots of big partners in it.

And also small and large corporations, everybody from Lockheed and Boeing. Somebody's got to build the spacecraft. And all the instruments in the ground system, mission control, all of it. And so I'm going to ask you like cliche questions, like what most surprised you arriving at Pluto? 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. So the Antarctica Daily News? Exactly. I got a copy of it. It's not called that, but yes, they sent it to me from the poll. I said, it's every continent but

Antarctica on a radio show, and the Antarctic people got all upset. We covered it. 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. 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. So does this tell you that Pluto was plutologically active? Is there a word for the geology of Pluto? Very clearly. But it seems so little

and we don't think of tiny objects as having active geology. That's right. Is that a bias? It's a bias. The less of our 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, it was born yesterday. In other words, you age date because you have some expectation of what rate craters would accumulate. 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? Good, good. Versus some other piece of paper with more or less dots.

And so that paper would have been out there longer, right? Yeah. And in the case of Sputnik Planum, it's the scale of the state of Texas, and it was created yesterday geologically. Whoa, whoa. This little planet is somehow active after four billion years. Any understanding of that? Nope. Okay, so what people don't understand is scientists love being stumped. We love being stumped and we don't mind being wrong. Like,

we thought Pluto would be simpler. We were wrong. This is wonderful. David, so you're a planetary comparative planetologist, right? And so how would you compare Pluto's features to other stuff going on in the solar system? I didn't notice anything like it out there, but you've got a better mental inventory. 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 small.

Maybe it'll just be full of craters and not that interesting. But in fact, it's anything but. And there are features that are reminiscent of many other places, and yet there are aspects that are just all pure Plutonian and nothing like it. Maybe the most similar place is Neptune's moon Triton, which is around the same size and also a frozen outer solar system object that's largely composed of nitrogen ice. So are you saying they look alike?

So you've got some chemistry analysis of what's going on on the surface. I'd say that there's some similar features, but it's not like you would mistake one for the other. But you have nitrogen ice that's frozen nitrogen, I guess. What else do you have? You've got nitrogen ice, you've got traces of methane. Methane ice?

Yes. And also you have some features on Triton that are surely water ice, the sort of bedrock, the strong stuff on Pluto and also on Triton is water ice, kind of playing the role that bedrock, that rock plays. 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. Right. So you cook it with gas.

Cook it with gas, right. It's also the gas that we make ourselves. Oh yeah, out of your butt. I was going to say cows. Cows, okay fine. Cows, yeah, it comes out of their digestive system. Not ours, right. Exactly. It was a cow. So, but methane, 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? It's, oh gosh, minus 200, I don't remember the exact. Okay, so.

Really cold, really cold. But it's pretty darn cold. Yeah, you could have just said darn cold cold and that would have worked perfectly for us. So, also, beyond what the chemistry is, there's 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 different colorations? 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 planetology is like born yesterday.

There's no craters on that thing, 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 it, which is one of the cool things about these bodies is that they all have some organics. So it's a source of energy for methane to explore other chemical reactions. Absolutely, yeah. 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 okay now you know places 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 the pressure that we have here on earth wow yeah you still want to 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 read is one one hundred thousandth so your definition is clearly different from the person in the streets definition yeah i mean you know it depends on what you want to um

call an atmosphere uh you know maybe you want to call it a dwarf atmosphere. I don't care. 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. So if you were on Pluto and you sneezed, you

would actually get rid of the entire planet's atmosphere. You could probably sneeze some of that stuff right off. You could probably do it. Which is why astronauts should always, you know, bring some antihistamines when they go to a planet like that. 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? Absolutely. I think the most promising...

Yes? You would say yes to that? 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, probably on Pluto, it's radioactive decay that's moving around. Oh, so sources of warmth. Okay. 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... Okay, I think you're reaching for it there, I think. But here's one I'll grant you. Alright, in 5 billion years, 5 billion years,

the sun goes red giant, alright, 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? 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, when the sun continues to heat up as it is doing now and goes 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. Wow. So it's like planetary real estate. First rule, buy on the fringe and wait. Right, exactly. That's right.

But also, what did you hear what David said? The future's in the outer solar system. Did you hear what David said? He said it might get uncomfortably warm here on Earth. Yes. 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. Or we just go to another solar system. Yeah, but at least it's moving in the right direction if we go to Pluto. 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. Well, with the exception of Neil Tyson, it's convinced most people that it's a planet. Okay, I'm pummeling him now. I'm giving him a niggie on the thing. 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 say, I didn't know it was that big. Yeah, yeah, 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 they're planets alan stern has planet on the brain 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. There's two ways to go at it. You can go at it scientifically and scientifically the geophysical planet definition says that when objects are big enough to be round by itself gravity, 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 ten 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 in a logical way. It's not Pluto's problem. It's our problem. Well, Pluto's an inanimate object.

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 not so four percent of the International Astronomical Union was there four percent voted it was almost 50-50 and so about two percent 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. Okay, so now... And really get the experts in.

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, seven years ahead of that, running a very prominent exhibit at the American Museum of Natural History, you wanted to take Pluto and the small planets like it off the list of planets. Didn't you do that? 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 the Kuiper Belt. So if I go over to AMH today, I won't find any numbers like eight? Never. There was never the number eight. I was misunderstood. I'm having the best time. The press misunderstood me and

my team who did this. So Pluto's a planet. The institution did not commit to whether... I'm asking Neil. I think... This is where you get to make the news, Neil. 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 it's not a planet anymore. And I agree. And that's where I can meet you somewhere on the island. I like that. Dwarf planet is a category of planet. Just like dwarf stars. The sun

is a dwarf star. Would anybody deny it's a star? Yeah, it's a dwarf star. Most people don't know it's a dwarf star, but it's a dwarf. It's true. Yeah. Yeah. That's pretty good, Neil. Oh, we're shaking hands.

Uh-oh. On camera. Because Neil just said dwarf planets are planets. We can edit that out. You guys edit that out later. You probably will. No. Guys, I told you to edit that out.

Why is it still in there? Oh, my God. Let me just say, that is a deeply wounded man you're talking to right there. I mean, 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.

So, David, what's your take on all this? 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, and people don't stand up and go, wait, you know, they correct and go, no, you mean dwarf planet. That's because they've all been brainwashed. 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. Not all apes are human beings. So could it be something along those lines

when it comes to dwarf planets? 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 just to re-examine 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. That was a dig, you're saying. So what I did, because of

my episode dealing with the public and Pluto at the museum, I published a book called The Plutophiles, The Rise and Fall of America's Favorite Planet. And in there 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 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. 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 a habitable zone? Might it have life? Does it have an atmosphere? You have to ask me 20 questions after I hand you a classification that tells you the word needs improvement. So the classification is far too large.

Far too large. And so we should have 20 different classifications. 20 different things should be like rocky objects and gaseous objects, objects with rings, objects, and then find some words for that. That way I can say I found one of them, and then you're right there. Absolutely. I mean, we've always had gas giants and terrestrial or rocky Earth-like planets. It's already ready to happen. 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.

And I think they should have waited. We should wait until we get a nice, well-defined catalog of exoplanets 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. Nice. Well, I mean, yeah, the definition's going to be reworked and reworked again, because we're in our infancy of learning about exoplanets. And you know, the IAU, when they made this... International Astronomical Union. 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. 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. Well, coming up next, more about Pluto's largest moon, Charon. David, am I pronouncing that right? Charon? Yes. Good. Thank you. And New Horizons'

continuing journey into the Kuiper Belt when StarTalk returns. Welcome back to StarTalk. I'm here with Chuck Nice. That's right. And our guest via Skype, planetary scientist David Grinspoon. Dr. Funky Spoon. That's because that's his handle. That's his Twitter handle, Funky Spoon.

David, why are you funky? Well, you know, some of us are just born that way. Right on. As you know, I play music, too, in addition to different stuff. All right, we'll give it to you, then. We'll give it to you. I just can't help it. For now.

You're borrowing it. We need more evidence. We're 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. All right, for the longest while, we didn't even know Pluto had a moon. But you know what? Here's the thing. Before you get to that, because I know you teased that talking about Sharon.

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. Oh. Oh, yeah, because I got blamed. I know you got blamed. And you know what's funny? I hate to say this, but Alan our in earlier and when we heard in that clip uh-huh it was like you know you and your team neil right uh and it was almost accusatory the way he stopped short of it he stopped i have a file cabinet draw of hate pissed off angry

third graders whole classes the teacher teacher organized rebuttals. Look, I happen to have one right here. You got one? Yes, I do. Dear Dr. Tyson, you are a big poopy head. I remember that one. Pluto is my favorite planet. I was a poopy head in that moment. I was a poopy head at that moment. Yeah. So, and it's, yeah. So I was like the leading edge of this. David, do you, can I get some sympathy or something from you for that? Well, yeah, of course. You know, I was working at the Denver Museum when all this came down and I'd have kids, you know, freaking out and wondering what happened

to Pluto. I mean, it's mean, people get very emotional about it. 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. Okay, fine. Yeah, I think it's... What is it?

I think in America, that's why I subtitled my book, The Rise and Fall of America's Favorite Planet. Right. Because an American discovered it. And it was discovered the same year that Walt Disney first sketched the dog that would get the name Pluto. 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? Same time.

Around the same time. So the time you learn about the planet, you're learning about the dog, or you're admiring the dog. Exactly. So I think Americans had a little extra attachment compared to the rest of the world. I ask people in Europe, in France, I said, do you care that Pluto's, quote, demoted? I don't care. Are you kidding me?

Pluto is a peasant planet. Hey, Chuck, I got to tell you, it does upset me a little bit when you talk about Venus in that way. Of course it would upset you that way. I think there's something about it being small and kind of an oddball and maybe a little bit of an underdog. People were sympathetic with Pluto. It's actually a very interesting phenomenon. Well, plus, we would learn that Pluto had a moon in 1978.

A moon of Pluto was discovered named Charon. Charon! Charon, which was the name, 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?

Yeah. It was also the wife of Jim Christie who discovered Charon was named Charon. Oh, nice. Okay. It was kind of a twofer there. Some people pronounce it Charon, but Charon works for me. And also, it's not only Charon, but it's got four other moons. So Pluto has at least five moons. Is that correct? 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 there was this whole hazard avoidance sense that we really got to make sure there aren't any other small objects in orbit around Pluto. That would be embarrassing. You know, something really tiny would doom the spacecraft at those speeds. But all they found was this one giant moon, Charon, which we already knew about. And then these four smaller moons, which are named Nix, Hydra, Kerberos, and Styx. Wow, you're right.

Everything does have to do with death around Pluto. Yeah, yeah. 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 an 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. 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. Oh, because the moon itself is not very reflective. Our moon is kind of just dirt. It doesn't reflect very well, right? But Charon's icy and we've discovered that it had a really interesting geological pass.

It has the largest canyon system. 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. You mean our moon. Our moon, right. I just want to make that clear because people talk about how bright the moon is. I can read by moonlight or jog by moonlight, but it would be way brighter if it weren't so dark.

Exactly. Okay. Yeah. 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. Whoa, because Europa has a subsurface ocean. Yeah.

Yeah. Right? Okay. 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. 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 is below the crater rate splashes up it excavates that excavates that material and Sharon's got this enormous Canyon system that dwarfs the Grand Canyon it's just another cool place I think we need to rename our Grand Canyon because now that we've got a there's the Mars you know everybody's got everybody's got a canyon bigger than Earth what do you think we got it we got a canyon bigger than Earth. What do you think? We've got to rename this. Even Pluto and Sharon. Yeah.

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

It's a somewhat impressive canyon. So, David, what else can you add about Sharon? Well, Sharon is another delight. Even on its own, it was almost worth 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 the moon. Because Alan said it's kind of an anti-ice cap, right? Yeah, yeah, exactly. And there's some suspicion that might have to do with exchanging gas between Pluto and Charon, if not at present, maybe in the past.

No, no, that system is tipped, right? That orbital system is tipped relative to Pluto's plane of orbit around the sun. Is that correct? Yeah, exactly. But of course, it's tidally locked now. So if you were on Charon, there'd be one place on Charon where Pluto would always be overhead, and you could just stay there and go around and watch Pluto go by. In other words, Charon does not rotate relative to Pluto. Yeah. Yeah. It always shows the same face. Yeah.

Mm-hmm. Yeah. Wow, that's pretty cool. It's very cool. So it's double tidal lock. Double tidal, yeah. Did I tell It's very cool. So it's double title lock. Did I tell you? Did I tell you in high school? No. I didn't tell you? No. I didn't tell you? No. Okay. In high school, I wrestled

in high school. Well, that I knew. Okay. I was undefeated, and I was captain. Okay. I was kicking some serious ass, and I wanted to invent a new wrestling move called the double title lock. Doesn't it sound like a move that has to have that name? Right. Okay. But I never perfected it, but I'll show it to you later. No, don't show me.

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 never really agreed with that connection. Maybe you can bring me on board. I don't know if I agree with it either strictly, but the logic is that 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. Earth's is rather extreme. Pluto's is even more extreme as being a fraction, a sizable fraction of the moon to the planet, Earth's is rather extreme. Pluto's is even more extreme as being a fraction,

a sizable fraction of the planet. In fact, for Pluto and Charon, the middle point of their gravity is outside of the physical body of Pluto. It's a double planet. It's basically a double planet. Damn, he got me to say planet. I was just about to say.

You just said planet. This is a diabolical plot. Okay, go on. The idea on Earth is that the moon stabilizes Earth's climate by acting almost as like the outrigger on a canoe by preventing the axis of Earth from wobbling more. And 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 somewhat more wobbly climate. I'm not sure.

But that is the idea. I did not know that. So the moon, our moon acts as a keel, kind of? In a way, yeah. That's amazing. That's exactly right. A gravitational keel. I would say, look at the temperature range over which we survive or even thrive anyway on Earth. We have humans living in the equator. Eskimos living in the Arctic. So I don't

think that we would fear that. I agree with you. I mean, you can imagine somebody looking at our planet from some other kind of planet and going, oh, look at these seasons. They have winter and summer. Nobody could possibly live there. It may just be that kind of argument. Okay, cool. So New Horizons went by Pluto and it kept going on a flyby and it's 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. 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 4 billion years old. It's always been in the deep freeze, so it's scientifically a great sample of that early era. Okay.

It doesn't have a really good name yet. 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. So we'll do better. We're going to have a naming contest with NASA and pick something. Good. So that's going to be another flyby. That'll be a flyby. And we know when. It's a very easy date to remember. It's January 1st, New Year's Day, 2019. 2019. Okay. I'll put that on my calendar. And again, you're flying by. Do you have fuel for yet a third destination? Probably not, but we have plenty of fuel to run the spacecraft on a

Voyager-like mission way out to the helix. Oh, okay. Because that uses less energy, of course. Yeah. Yeah. Yeah. And of course, you've got, this is the fastest spacecraft ever launched from Earth. It is. And you will leave the solar system the way Voyager did. Exactly. Okay. Will of course, you've got, this is the fastest spacecraft ever launched from Earth. It is. And you will leave the solar system the way Voyager did. Exactly. Okay. Will you ever overtake Voyager? No.

Oh, that's too bad. And a lot of people wonder why. If it was the fastest launch, how was Voyager ahead and staying ahead? Because Voyager cheated. It got some extra boost from Jupiter, I bet. It got four boosts. Four boosts? One from each giant planet.

Oh, my God. I didn't know it was on four? Yeah. Oh, my God. And we only got Jupiter. So they're a little faster than us. Okay. But that's fine.

Okay, so this is stealing some of the orbital energy of a giant planet, and you get a little boost out of that. Okay, that's fine. I don't think the planet's mined. I don't think they notice. They're inanimate objects. So David, tell me something about the Kuiper Belt.

Is it real enough, and it extends out there? So David, tell me something about the Kuiper Belt. Is it real enough and it extends out there? Yeah, yeah. I mean, the Kuiper Belt is this vast outer realm of our solar system that we really didn't even start to learn about until the 1980s and 1990s. By the way, 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 a species of object, right? Absolutely. That was the discovery that led to this whole question of reclassification was the fact that there are lots of objects out there, not just Pluto.

And that led some people to say, oh, well… How many is lots? How many is lots? Oh, gosh. By the way, when you're funky, you can't use the word gosh. Just those two. Well, damn. There you go.

That's funky. Gosh, darling. Golly gee. Diddly doo. I'll tell you, only bar in that funky moniker. You've got to keep earning it. But go on. There are millions of objects in the Kuiper Belt.

You know, 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 vast. And you call them objects, but we can call them comets. They're icy, right? Yeah, well, I mean, exactly. I mean, if you took them into the inner solar system, a lot of them would call them comets they're they're icy right 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 like pluto would do yeah go on and you know the larger ones are uh 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 a vast realm. 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 concentrated along that plane where the planets all... 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. I mean, it's a thickened belt. 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 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 planet's orbiting. So this will go on for another, how much power does the thing have to keep going?

It's supposed to, you know in terms of it's it's got a plutonium power source and um quaint isn't it it's plutonium plutonium yeah we said plutonium past pluto yeah yeah not uranium that would be a uranus thing it's going to slowly lose power but it's going to last for decades probably at least until the 2040s. 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. And just if I remember correctly, you cut your teeth on Voyager, didn't you, back in the 70s and 80s?

Yeah, I was a student, an undergraduate intern at the Voyager Jupiter encounter in 1979. It was a really life-changing and mind-blowing experience. Wow, we have so much in common. I watched every episode of Star Trek Voyager. Yeah, pretty similar. And you would have had, that might have been

your first encounters with Carl Sagan at the time who was active with Voyager? Yeah, yeah. Sagan was a mentor of mine then and just 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 wide-eyed undergraduate kid, you know, that was a pretty mind-blowing experience. Nice. Well, when we come back, we're going to talk about Planet 9.

Hmm. What is that? Ooh. Ooh. It's a hypothetical planet. Could be hiding in the farthest reaches of the solar system. When StarTalk continues. we're back on star talk with my co-host jack 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. Now, earlier this year, since, David, we got you online and you were outer solar system guy. We got you online, and you're an 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. We don't have to worry about whether or not this is a planet. Exactly. Exactly. 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 around the sun.

So I had to ask Alan because he's... It's a long day, man. It's a long day. Oh, that's a year. Sorry. Phil, one revolution would never turn revolution. You 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. Tell me about Planet Nine. Pluto? I'm pummeling him again. Let the record show. I was widely quoted. Actually, I think it was Nadia Drake that did the article that asked me about that designation,

which I really think- See, that's a beef between you and Mike Brown. I think- Mike Brown named it Planet Nine, right? 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.tech professors can't count. That became a hashtag.

Caltech can't count. I missed this. Was this in a Twitter war? Just a couple of weeks ago. Oh my gosh. Yeah, it was a Twitter war. Okay. 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. 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. Yeah. And it's mysterious.

With the X-Files. Yeah, 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? Are you talking about Pluto again? No, I'm talking about Planet 9. Oh, Planet X.

We're not going to call it that. Not today. He's not going to call it that. No. What would you like to call it? Planet X. The object Mike Brown called Planet 9, which I'm happy to call Planet X. Thank you. Okay. Could you comment on the method of how that was inferred? So it hasn't

been discovered. Not directly, right. And there've 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. So David, I looked at the research paper that made this announcement. It seemed pretty legit to me, using sort of gravitational... Calculations. Thank you.

No worries. That's what I'm here for. So you do the inverse calculation for the gravity equations. Normally you say, here's the mass, what is the force of gravity at some point? Right. But instead what you say is 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. That's basically

what they did, David, correct? 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. Where did they come from? Well, 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. It was this tossing out of planetesimals of the little planets, and some not-so-little ones got shuffled around as well. 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 cast-away debris from what was going on from within the inner solar system. Yeah, I mean, well, 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... It's our inner solar system's junkyard, basically. That's what you're saying. It's our inner solar system's junkyard. So it might have... So there's 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 yeah i think there there should be based on what seem to be the best theories we have of solar system formation and And it may be that this specific prediction, even if it's wrong, will lead us to other things. I think we will find more planets out there. So is this going to give us another source of predicting mass extinctions on Earth? That this thing only comes around every 10 or 20,000 years? That it'll disrupt Kuiper Belt comets and send them raining down on Earth?

Well, it could. I mean, you're referring to, you know, there was this idea of Nemesis, which 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 think the evidence that there's a periodic signal 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. So I'm kind of skeptical of that just because I don't see the signal in the data of Earth.

So it turns out, in addition to Planet 9, Alan Stern told me Planet 9 could just be, excuse me, Planet X. Planet X, right. Planet nine could just be excuse me planet X planet X right could just be the tip of an iceberg of Many many larger planets in the outer solar system. Let's check it out 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 think ones like Neptune size certainly earth-sized yeah the models suggest that earth-sized planets in the Oort cloud are a good bet mm-hmm so we should watch that space yeah we absolutely should it'll be exciting yeah 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 and who knew in the 20th century that the solar system was so good at making so many planets? And are some of these planets, do we think, escaped from the inner solar system and they're just sort of wandering out there? 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 york cloud it threw a lot of comets out of the solar system altogether it threw the 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 york cloud i didn't know that oh my god why not i mean in fact there's a theory that some dynamicists 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. So once again, thrown up there, and we're going to go find it. So the more we learn about it, the more nuanced and the more complex it is.

And that's a good thing. Yeah, I think so. David, give me some final reflections on all of this. 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. 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. Right. Yeah. And it's a sphere. From a distance it looks like when you say a cloud of bees. Right. Same kind of thing. Same thing. 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 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 oar cloud comet because that's the only thing that actually has comets that can come from that direction. That's right. Right, right. So, Chuck, what do you make of all this? 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. So, Twitter wars over things other than Donald Trump's hair. Exactly. Yeah, I think that's great. What I like about it is 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. Absolutely. And 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? Yeah, it'll be a flyby. It's like, what are you doing in my neighborhood? Right. I thought I told you never to come around here. I want to see what's going to happen if a Neptune comes flying. But what would be cool is if some of those planets still had a residual

heat source, such as Earth still does, and if that's the case you could have life possibly evolving on planets on a totally rogue planet. On a totally rogue planet. And they will know nothing of a host star as they wander through space. We don't need no stars.

We don't need no stinking stars. We don't need no stinking stars. David Funky Spoon. David Grinspoon, thanks for being on StarTalk. Thanks so much, man. And again, welcome to the community of StarTalk All-Stars. I look forward to seeing you in many ways and times. Thanks a lot, Neil.

And Chuck. Yes. Always good to have you, man. Always good to be here. 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.