Daniel and Jorge Explain the UniverseDaniel and Jorge talk about the vast and amazing Oort cloud, and whether it is throwing snowballs at us.
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Podcasts presented by State Farm like a good neighbor. State Farm is there? Hey, hoorge, what's your favorite Solar System object?
I'm gonna have to go with the Earth because you know it's the only one I've.
Been to, so you're not a gas giant kind of person.
Depends how many tacos I had for lunch. But what about need? Do you have a favorite?
I'm a big fan of the Sun and and everything it does for us here on Earth, But my favorite thing in the Solar System is actually comets.
Comets. What have comics done for us?
Well, they're like cosmic snowballs, and actually most of Earth's water turns out to be melted comets.
I guess water's pretty useful to have. Wait, are you saying the Solar System is having a snowball fight.
Yeah, it's more like deadly planetary dodgeball.
I am Warhamm, a cartoonist and the creator of PhD Comics.
Hi.
I'm Daniel. I'm a particle physicist, but I have strong opinions about various Solar System objects.
Welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we talk about everything that we know about the universe and everything that we don't know about the universe, everything that makes us wonder, and everything that makes us go huh. And we explain all of it to you because we think that your curiosity is as valuable as the curiosity of scientists working on the front line.
Yeah, and there's a lot to be curious about. The universe is full of amazing and incredible things and a lot of mysteries, a lot of things that we don't know where they come from, or what makes them what they are, or why they're there.
Yeah, and a lot of great scientific discoveries begin with pretty simple questions, you know, like why is that thing there? Or why are those comments flying? Through space and where do they come from? Is one of them going to hit us and wipe us out. Great scientific discoveries come from really simple questions that everybody wants to know the answers to.
Yeah, because we have questions even about our own backyard. Our Solar system is still full of things that we don't quite fully understand.
Yep. People like to talk about things in the distant universe that are still a mystery. We don't know how big it is or what's going on out there in the depths of the universe. But you're absolutely right. There's still a lot to be discovered right in our own neighborhood, big questions about what's going on in our own household that we still don't know the answers to.
So, Daniel, you have strong opinions about things in our Solar system. Are they all positive or are some of them negative? Is there someone you don't like here in the Solar System?
No, they're all positive. I love everything in the Solar System, from ice giants to planetismals, to space centaurs, to deadly comets to enormous burning balls of gas. I just think it's all pretty awesome. I can't imagine having a negative opinion about anything.
Do you include in that all the people on Earth too?
Yes, I love everybody. No, it's incredible when you look out there in space that you see so many beautiful, amazing things. Like when was the last time you looked at something out in space and you thought that's just kind of a you know, it's all just sort of like incredible and beautiful. You know, whoever the universe as visual artist is, they're doing a good job.
Yeah.
Although you know, we live in California, so right now when I look up at the sky, it's mostly smoke.
Well, then take a journey through the Solar System with your mind's eye.
Yeah. There are a lot of big questions about the Solar System and how we got to where we are. And one of those big questions about our Solar system is where do comets come from? We don't know of a comet factory here in our Solar system, do.
We We don't know of a comet factory. It could be that there are aliens out there in the outskirts of the Solar System packing up ice balls and shooting them at Earth. Or it could be that they come from something else, something deep out there in the Solar system. That's basically a huge reservoir of comets ready to fall in, screaming towards the Sun and boiling up.
And this is a big question because some people think that most of the water on Earth came from comets.
That's right, Comets are mostly ice. You know, something a lot of people don't understand about the universe is that water is not rare. We talk about liquid water being something we're looking for in the surface of planets to see if there's alien life, but water as a chemical, there's tons of it out there. There's like planet sized blobs of it. So most comets are icy planetismals. They're just big balls of ice. And some of them felled towards the Earth in the early days and landed and melted and formed our oceans.
Yeah, thank goodness, because that's where life came from. Right, had them in for those snowballs, and we wouldn't be.
Here, that's right. So next time you put your lips to a glass of melted comet, remember you are drinking the outer solicits.
You are melted common right.
Yeah, next time you go somewhere and order a drink, order sparkling melted comet and see what they do.
Yeah, so a big question is where they come from. And so scientists have a potential answer to that question, right, Daniel.
That's right. They don't know for sure. Nobody's ever actually seen it, but we've given it a name, so to they.
On the podcast, we'll be asking the question, what is now, Daniel? Is that pronounced ort or ort? Because it's spelled o rt.
It's a great question, and it's a Dutch name. It comes from a Dutch astronomer who first thought it up, and so I reached out to my Dutch speaking brother to ask him for his preferred pronunciation because I didn't know is it ort ort ort or some like weird Dutch vowel that we don't even have in English that can never be replicated?
Keep going, keep going?
Well, you know there are vowels in Danish that you know, you can only replicate if you get like punched in the gut in exactly the right way, like you danged speakers out there know what I'm talking about. But it turns out that or it spelled o rt is pronounced like port.
Mmmm. All right, So it's a cloud apparently of some sort, and it's I'm guessing it's out in space, and so a big question is how many people out there know what it is and what its significance is.
That's right, So I pulled our listeners who have volunteered to answer random Westin's over the Internet from a physicist they've never met. If you'd like to participate in such absurd commentary on our physical universe, please write to me to questions at Daniel and Jorge dot com. And thanks to everybody who shared your speculations.
Think about it for a second. If someone asks you what the or cloud is, what would you answer. Here's what people had to say.
The Orc Cloud is one of the outhermost regents of the Solar System, comprised of we think a bunch of remnants of the early Solar system.
The Orc Cloud is a group of like dust and rocks and asteroids and just material that's way outside and circles our whole Solar system. I think in a giant sphere, or maybe just a circle.
The or Cloud is a vast array of comments and other such icee borning around the Sun, very far away from the rest of the planetary systems.
I know that the Sun it's the middle of it, and it passes our solar system, so passes Pluto. Is it the big.
Cloud of dust that's I'm spewing out the top and the bottom of the milky Way. I didn't have anything to do with the quipper Bell. Probably close to the solar system.
I think the Oort cloud is like an area outside the solar system where there are some icy objects.
I'm not sure what, probably comets and things like that. All Right, some pretty good answers. Most people seem to know it's something related to our solar system and that it's a cloud, and that maybe there's ice in ball.
Yeah, exactly. It's something big and fuzzy and out there and cool and cool and cool. And my favorite thing about the ord cloud is at the acronym the OC is the same as the place I live, Orange County.
Except it's a little warmer.
I think it's a little warmer, but it's also still very very cool.
That's the first time I've heard you give a compliment to the Orange County there.
I love Orange County. Best place in the world to live. Seriously, what could you complain about? Well, that's not the topic of today's podcast. We're talking about the cosmic OC, the Solar System's OC, not California's OC.
And so it's apparently something out in space. And so Daniel, let's step people through it. So what is the Orc Cloud?
The Orc Cloud is super awesome. It is a theoretical cloud of icy planetismals or mini planets planetismal.
Did you just make that up? Or is that the actual science term?
Oh?
Man, I wish I could have made that word up. There's something wonderful about just saying that word planetismal. Right, but no, planetismal is a mini planet and it's smaller than a dwarf planet. Right, you got planet dwarf planet and then planetismal.
They couldn't just say mini planet.
Well, it's sort of like Planetino, you know, that's what you do it English, Tito. And so it's a bunch of these and they're really really far out there, Like if you have the Solar System, you know, the Earth is at one au we call it an astronomical unit, and you go really far out you get out to like Neptune and Pluto. You have to go much, much, much further before you get to the Oort Cloud.
Is it even considered our Solar system or is it technically outside of our Solar system.
Yeah, it's a great question. Most people consider the end of our solar system to be just under about one hundred AU, where the Sun's radiation becomes dominated by the galactic radiation. Now you think of space as sort of like empty, right, but actually it's filled with streaming particles. The Sun is pumping out particles, not just photons, but protons and electrons and all sorts of crazy stuff, and it dominates the region around it with all of its pulsating radiation. But the rest of the galaxy also has a wind that's coming from all the other stars in the central black hole and all that crazy stuff. So we define the edge of the Solar system, it's called the helio pause, as the place where the Sun's radiation stops dominating the local environment and you're taken over by the galactic wind. And that's like one hundred or so AU.
It's like when our Sun becomes just another star kind.
Of yeah, exactly. And the wind from the rest of the galaxy takes over the Sun's wind. And here again we wind. We don't mean air, We just mean the particles that it's shooting out. But the orc cloud starts like ten times further out than that, like at a thousand AU.
Now, is this still sort of like bound by the gravity of the Sun or is it pretty much like an independent thing from our Solar system.
It's definitely bound by the gravity of the Sun. So if you define the edge of the Solar System by the radiation, it's like at one hundred AU. But stuff that's further out is still gravitationally bound to the Sun. But it's a little bit loose. It's like a little fuzzy. It's so far out from the Sun that it's not that hard to knock something off and have it escape into interstellar space.
Mmm.
So it's not orbiting around us. It's sort of like we're tugging them and it's tugging us.
It's definitely orbiting around us. Think of it like a huge shell surrounding the Solar System. The other fascinating thing about it is that it's not a disc, right. Most of the stuff in the Solar System is a big disc. It's flat. But the ord cloud, we think is a sphere. It's like totally surrounding the Solar System, and it goes out really really far out to like a light year maybe two light years of just this like cloud of little frozen objects, and there could be like trillions.
Of them, manillions of planetmal trillions of planetismals mini planets I'm sorry, yeah, planet detos. And it's sort of like calculus.
You know, in calculus you sum over infinitismals and you get like an actual quantity. In the same way, if you sum over all the planetismals in the ord cloud, you get a combined mass of stuff that's like five times the mass of the Earth. But then again spread out into like trillions of objects.
Right, and its spread out and not just like a wide but tall too. Like it it's pretty diffuse.
It's very diffuse. Like it's not like flying the millennium falcon through an asteroid field where you're like dodge and weave right, it's like, could we see something, like is there one there? It's so far out there, it's mostly empty. But again, they are gravitationally bound to the Sun and they are orbiting the Sun. That's why they are in a cloud around the Sun. It's not like just the whole interstellar medium is filled with these objects. It's a cloud of them. We think again, we think, we don't know for sure we haven't seen them because they're so small and far away, but we think that they're there in this big blob around the sun.
See, and it's made up of like giant literally like giant balls of.
Ice, basically snowballs. How big, Well, each one could be like bigger than a kilometer in size, So we think that there are like trillions of them that are more than a kilometer, and maybe only billions that are twenty kilometers or larger. But if you wanted to have a cosmic snowball fight, that's like where your arsenal is, that's the place to go for the stockpile.
Wow, So that's like a let me see, that's like a snowball about the size of Los Angeles right kilometers.
Yeah, there are billions of frozen Los Angeles Is out there in the OC.
Because they are pretty cool, icy cool.
They are pretty cool, and if they weren't gravitationally bound to the Sun, they would just sort of float away into space. But they are bound there. They're floating around, but you know, it's sort of loose, and so sometimes the thought is sometimes something perturbs them and then they can get knocked out of their very loose orbit and plummet towards the Inner Solar.
System because they're in a stable orbit. Is that the idea is that they're like happily going around our Sun in this huge, wide orbit, but sometimes they can fall in.
Yeah, we think it's probably stable and if nothing perturbed them, they would just happily hang out there really far away, staying frozen. But you know, we are in a little neighborhood, and since it's sort of loosely held by the Sun, it's not that hard to perturb them, and you can have things like galactic tides that squeeze the Oork Cloud and knock some of them out of orbit.
You mean from the center of the galaxy.
Yeah, just the way the Moon has a gravitational effect on the water of the Earth. So as the Moon goes around the Earth, it tugs on the oceans and causes tides. We have a gravitational pull towards the center of the galaxy, and that tends to tug on one part of the Oort Cloud that's closer to it more than the rest of the Oort Cloud, so it sort of extends it. And then as we move around the center of the galaxy, very slowly, you know, hundreds of millions of years. The direction of that tug changes, so it's a dynamic. So as we move around the center of the galaxy, the tides change, the galactic tides change.
So are we right now on high tide or lord tide?
Well, we're at the center of it, right so we wouldn't feel it at all. But there's a blob of the Oort cloud that's always pointed towards the center of the galaxy that would be at high tide. There's more objects in that part of it, so we're sort of at the very center of it, so we can't tell. But it can be galactic tides. It can also be like nearby stars. If a nearby star happens to come somewhere close to us as we all swish around the Milky Way, it can perturb the orc cloud and send comets falling in towards the center of the Solar system right.
Or steal them, possibly steal them.
Or steal them absolutely, and we'll talk about where these came from. It's not clear that all of them actually came from our solar system.
Oh wow, And I guess the thing is that we've never actually seen this cloud, right, Like, we don't have pictures of it or even like radar of it or evidence of it.
That's right, it's so far out there that it's still theoretical. There have been some glimpses of one or two objects that people debate might be like part of the inner, inner, inner Ort cloud. But these things are really small and really really far away, Like it's hard to see Pluto, right, And Pluto is really close compared to these things, And nothing that we have out there in the Solar System has gotten anywhere close to them. Like the thing that we have sent out into space, that's the furthest object the humans have ever built. That's Voyager one, the fastest human spaceship ever. Right, that thing won't get to the beginning of the Oort cloud for another three hundred years.
Well, Daniel, I don't know if I believe in this thing or not. But let's get into how we know it's actually there and why we think it's important for our origin as a planet and as a human species. But first, let's take a quick break.
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All right, we're talking about the Orc Cloud, which is I guess, Daniel, you would subscribe it as like a giant shell of city size snowballs floating out hundreds of light years away from the sun.
That's right, And snowballs makes it sound quaint and fun and like if you get hit by one, you can just go inside and warm up with a cup of hot cocoa. Right, But these things are massive ice balls, and if one of them hit the Earth, we might be toast. So we'll talk about the danger of these things later on, but I want to make sure people are aware that these are basically massive space bullets waiting to hit the Earth.
It's like a real snowball.
If they pack enough ice into that slush ball, it can really hurt.
Yeah, all right, So how do we know that it's actually there, Then what makes us think that there is this giant cloud of snowballs in space?
Well, it comes from sort of a paradox. In the last hundred years, we've established that there are lots of comets, but the Solar system is not very young, and so people have been wondering, like, where do all these comets come from? Because comets are not stable. Like, once a comet starts falling in towards the Sun, it loses a lot of its mass as the Sun boils it away. So a comet can't like zip around the Sun for billions of years. It only gets like, you know, fifty or one hundred, maybe two hundred times around before it gets boiled away. Right, So if that's the case, if comets don't last very long, why are we still seeing comets.
So you lived in Arizona, and every once in a while somebody throws a snowball at your house, You're like, this is recent, Like somebody just made this.
Yeah, Or you know, if you're walking around your neighborhood and everybody's eating ice cream, you're like, where's the ice cream truck? It must have just come by, And so exactly, they thought there must be some sort of source of these things. The other clue was that there's sort of two types of comets. There are short period comets, comets that have an orbit around the Sun that's like less than ten Au, and these are mostly aligned with the Solar System. It seems like they're like basically Solar System objects, just blobs of ice somewhere in the outer reaches of the Solar System. But then there's a second group of comets that call long period comets. These are ones that have an orbit that's like one thousand Au or more, and they take a long time to go around the Sun, and they don't follow the plane of the Solar system. So these were really the mystery. They're like, where are these long period comets coming from? They couldn't explain it. They shouldn't stick around. And so to explain where the new ones were coming from, they said, maybe there's a huge blob of them somewhere out there beyond where we can see.
Oh, I see, you're saying, these long period commets, they're sort of coming out of left field. Does it look like they're hanging out with us or have been hanging out with us for a long time? It's like they're coming from somewhere else.
Yeah, because they can't last for very long. Like, once you see a comet, you're seeing it in the end of its life cycle. It could have been hanging out happily for billions of years deep out there in the Solar System. But once you see it, that means it's falling towards the Sun and it's going to get boiled away as it goes around the Sun, and it can't survive for very long. And even if it does make it one hundred or two hundred orbits, it's got a high chance of getting kicked out of the Solar System being perturbed by the gravity of one of the outer planets. So once you see a commet, it means it's in its last chapter of its life in the Solar System. So if we're still seeing comets four and a half billion years into the story of the Solar System, there has to be some fresh resupply every once in a while.
I guess if you're seeing a comment, that means it's getting hit by the rays of the Sun, which is probably melting it.
It's definitely melting it, and that's where the comet's tail is, right people like to imagine the comets tail is like the little action lines in a cartoon that show you where it's moving. But the comet's tail is not actually pointed away from the direction of the comet's motion. It's point away from the sun because the tail comes from the sun boiling away all the stuff on the comet.
Yeah, that's the signature tale of comets. That's what it is. It's not really a tail. It's more like a haircut. Is that what you're.
Saying, Yeah, precisely. And comets can actually have multiple tales. They can have tails going in different directions based on like the stuff that's in there that's getting boiled away, different compositions. So it's pretty fascinating to look at the tails of comets. It's pretty awesome.
Okay. So then someone named Jan Ord in the fifties said, hey, maybe all of these weird long period comets are coming from a very specific place. And so he came up with this idea of the org cloud.
Yeah, and he looked at the orbits of these comets and he said, how far out does it have to be to generate comets with this length orbit, these long period comets, And so that's how he estimated it. He made a very rough estimate for you know, how far away should be. And since then we have much better data, better telescopes. We can see the orbit of these comets much more clearly. We have more telescopes, we have hubble, and so we can track all this stuff and we have better estimates for what's out there and how big it is. But the basic idea came from this guy yan Ort in nineteen fifty. And you know, it's pretty awesome to get to put your name on the biggest thing in the Solar system, Like this thing just dwarfs the rest of the Solar system.
Did he call it the Org cloud or was it named after him?
That's a great question. I should read his original paper to see if he put his own name on it or if he was humbled.
Yeah, maybe called it the cloud a tesimal and somebody say that's a ridiculous name. We'll go with Org.
Yeah.
And it's fascinating and it's cool because it answers a question. Right, It tells you, oh, that must be where these comets are coming from. But like everything in science, when you answer a question, it opens up more questions, like, all right, well, where did this ort cloud come from? Why is it there? Why aren't they just closer into the rest of the Solar system. And that's an active area of research right now.
So we actually haven't seen this cloud. We're just sort of tracking where comets come from, and we think they come from this cloud.
Yeah, we have not seen this. We don't have telescopes that are powerful enough to spot it, none of our probes are anywhere near it. But it's sort of the best explanation and we have for the source of comets. So it's pretty well accepted in the astronomical community that it exists. Like we always like to see direct evidence of something before we conclude that it exists, like there was evidence for Pluto before we spotted it in a telescope. But you don't really claim discovery of it until you actually see it, right, It's like finding the body in a murder mystery. But sometimes it's the best you can do for a while, so we can talk later about like plans people have for how to spot the org cloud and to study it, but for now we have no direct evidence of it.
I guess it's not a thick enough cloud that it makes your view hazy, or you can see some of the like the light getting filtered through it.
It's not that thick, No, it's not that thick. These things are very small and very far away, so thick is definitely not how you describe it. There's enormous, vast empty spaces between every object in the ork cloud. Even though there are trillions and trillions of objects. The space we're talking about is incredibly vast. Right, We're talking about a sphere that's basically a light year in radius, and so there's a lot of space in there to distribute to trillion objects and still have lots of room in between them.
All Right, Well, I guess, like you said, a big question is where did this org cloud come from? Like why is there all this water deposited in one spot out there in the Solar system beyond the Solar system.
Well, as usual, we have a few theories. We have sort of like the most boring theory and then the most exciting theory, and the most boring theory is sort of a story of the formation of our solar system. Like we start from a big cloud of molecular gas and dust and stuff that collapses and you get the Sun and you have a disc of stuff that has too much angular momentum to collapse into the Sun, so it spins around the Sun without forming part of the star. And that's the protoplanetary disc, right, And there you have ice and gas and dust and all kinds of stuff that starts to form planets and clump together and form all sorts of stuff. The idea is that not everything clumps together to form a planet, like you have asteroids for example. If smaller things, gravity doesn't succeed at clumping everything together. But you do get big gas giants out there, like Neptune and Urinus and Saturn and Jupiter, they start to be sort of like heavyweights of their own gravitationally, and they can perturb the other stuff. And so there was a bit of a dance in the early Solar System as these big planets were finding their place, and as they move around they affected everything else. So the short version of the story is that we think that they were essentially tossed out of the Solar System by some of these gas giants.
As they were being born. These planets sort of like muscle their way around the craziness of the Solar System.
Yeah, and one of the definitions of planets if you believe in, you know, silly astronomical categories. Is that it's cleared its own path around the Sun. And so that's just sort of like the job of growing up and being a modern planet is that you had to like toss the little bits out of the way, or you know, slave them and make them into your moons. But in this case, most of the stuff we think was tossed out sort of in the early days of the Solar System formation. And it also it had a reverse effect. Remember, gravity is always two directions. So we think that one of the reasons that Neptune is as far out as it is is that it got tugged out by these objects as they were leaving the Solar System.
I guess one question is if a planet is kind of plowing through and sending things out into space, wouldn't it send all kinds of things like asteroids and rocks and gas. How did all this ice come together so purely? I guess, like, you know, why isn't it a mix of all other things?
Yeah, that's a great question. It is mostly a mix, right. These things are not pure water. It's not like you go out there and you find these pristine cubes of ice that you're ready to chisel out and put onto your space cocktails. These things are dirty. It's definitely still rocks in there. But remember that a large fraction of the stuff in the outer Solar system is ice, like you call uranus and neptune. They are called ice giants, and so it's something of a matter of how these chemicals are distributed through the solar system, like where water ends up and ends up freezing and gathering together. But a lot of the stuff in the outer Solar system, a non significant fraction of all the mass in the outer Solar system is water.
I guess out there most of it is ice and liquid, because if it was closer, it would evaporate and maybe blow out exactly.
So it's some complicated arguments about where stuff in the solar system collapses and what falls in and what doesn't. But you end up with a lot of ice in the outer Solar system. But these things are not pure water. Again, they're definitely bits of rock. I would not recommend drinking an ort object if you found.
One unless you like rocks.
Unless you like your cocktails dirty.
You guess they're a dirty snowball. All right, So that's one theory about how it form is just like a you know, a byproduct of the dynamics of the Solar system. What are the more interesting theories.
The more interesting theories are the interstellar theories. One idea is that our Sun when it formed, wasn't on its own. You know, we've discovered really recently that a lot of stars there was a twin. Yes, we're born as twins. That binary star systems are much more common than we imagined. So it could have been that our son had a twin and that this collapsing cloud of stuff formed two stars instead of one. But then these two sort of drifted apart, as you know siblings sometimes do, and there was a lot of material exchanged, and that gives you an opportunity to sort of pull material further away from the Sun because you have this big, heavy object, the other star, tugging on your solar system.
What so, what happened to this other star, sister star.
It's the subject of a Netflix documentary, you know, where they're going to reunite the stars for a dramatic conclusion at the end of the universe. That's right, not true crime, but true physics. No, we don't know. It's just hypothetical. We don't know that the Sun had a twin star at its birth. It's just an idea. But if it did, it could have been pulled off and gone in any direction. It's been a long time, it's been millions of years, and so it's hard to trace. It's not like the nearest star is necessarily a category for our lost twin. This thing would have been moving for a long time. It could be anywhere at this point.
And so the idea is that the sister star pulled some things from the Sun and then left it out there where the orctod would be.
Yeah, just like we were talking about the gas giants tossing stuff out of the solar system, now you have a much bigger object, a heavier object, another star even further out. It's going to tug out some of these stuff in our solar system to have a very large radius. And then as the two sort of separate, I'm imagining like you know, cell mitosis. Here two stars are pulling apart from each other, and it's sort of like threads in between them, and then as they get far enough away, they stop affecting each other gravitationally. And things settle into place, but you have stuff out at a pretty far radius because of the gravitational pull of the other star.
Interesting, so it was like the leftover from the divorce or something. Yeah, just got dropped there in the middle of space.
That's right, the poor abandoned objects in the stellar OC. So many divorces in the OC seems appropriate.
All right, let's get into our last theory about where this orc cloud came from and what it all means. The first let's take another quick break.
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All right, Daniel, There's a giant cloud of snowballs out in space about three light years away from the Sun, and we think that's where commets come from. But the question is where did this cloud come from? And so you have one more theory for us about that, and I'm gonna guess it involves eighties.
It involves alien stars, though we don't know if there are aliens enough living around those stars. The problem is that if you do the calculations and you have your theory of the Solar system and you predict how many things there should be in the Orc cloud, you get a number that's way too small. You get a number like six billion objects. But we know the number is much much bigger than that. So the idea is like, well, where do these things come from?
So wait, how do we know how big it should be? If we don't, we've never seen it and it's all theoretical. Is it just from like the frequency of commets that we.
Get exactly to explain the number of commets that we see, and they're radius and stuff, there should be a certain number of objects in the Orc cloud, otherwise we would see fewer and fewer commets. But if we try to predict how many things are in the Org cloud from sort of first principle's formation, like how many things should have been tossed out there by Neptune and Saturn and Urinus, then we get a much smaller number. So there's a discrepancy there. We know there are objects out there, we can't explain how they got there. So one idea is, well, when our star was forming, what was going on nearby. We talked about how maybe there was a sister star formed with us. But another idea is that maybe our stellar cloud that collapsed was near some other objects and it stole some material from those objects. That basically, the or cloud is like a lot of stuff from other solar systems that was stolen by our sun when it formed.
Wo it could be stolen. Good, Yeah, the water we're drinking could have been stolen from another solar system. Is that what you're saying?
You should feel guilty every time you have a drink.
It's illicit.
Well, it could basically be all omuamua, right. Remember Muumua was this interstellar comet, this frozen object path through our solar system, coming from some other solar system. And it could be that the Ork Cloud is basically just a bunch of these.
Oh I see, is that a theory that Omumwa came from the ork Cloud?
No Omuma. It definitely did not come from the oork Cloud. Its trajectory is totally inconsistent with that. We know that it came from another solar system. But it could be that the Orc Cloud is the product of stealing a bunch of Omumua like objects much much earlier, a long time ago, as our solar system was forming. So you know, possession is nine tenths to the law. Then you know, we've had these for billions of years. They're basically ours now, but there is a bit of original sin there, and having stolen them from another solar system a long time ago.
Well, yeah, I guess, because you know, I think the closest stars to us our solar system are about what is it like five light years away, right.
Yeah, three and a half light years away to proximate Centauri.
Yeah, so this orc cloud is about where those other stars are.
Yeah, it's the right order of magnitude, right, it's that big. It's so big that it gets you part way to other stars, and those other stars probably have their own clouds, and these stars tug on each other. One of the ways to perturb our oort cloud is to have other stars come nearby and give it like a little gravitational tug, which results in comets falling towards the Earth. Also, an oork cloud is not necessarily like a good thing. We talk about stealing this, but like it's a bunch of bullets hanging over our head. Where at the bottom of this gravity. Well, any of them roll down, they could totally wipe us out.
It's like deadly hail or something. You don't necessarily want that. It won't create a winter wonderland.
You want it early on, so it can give you oceans, but then you basically want to give them away to your neighbor so you don't have them anymore.
Wow. All right, So it is kind of like a giant interplanetary snowball fight almost, or tug of war.
Yeah, and that's where we think most comets come from. And you know, every time you see a comet that's come from the outer Solar System, it's been out there for billions of years, happily orbiting, not being close to anybody, being an and now it's screaming towards the center of the Solar System, maybe hitting a planet, maybe hitting the Sun, maybe just whipping around and going back out right.
It's kind of dangerous.
It's actually quite dangerous. You know. People talk about asteroids hitting the Earth and worrying about big rocks and planet killers and all kinds of stuff, But the truth is NASA has most of those figured out, Like most of the asteroids, the things in our Solar system, we could see them because they're pretty close. Certainly anything that's big enough to cause us any danger. And NASA has a great team of planetary protectors tracking these things to predicting where they're going to be and letting us know if they're going to be anywhere nearby. And often one of them slips through and we don't see it until it hits us, but that's because it's small. So a really big object that would actually cause any damage, NASA is pretty sure we're safe from those for a couple hundred.
Years because they're hanging out in the Solar System, so we can kind of see them, but we can see them. But if it's coming from outside the Solar System, then it can surprise us.
Yeah, if it comes from left field, it could be a a real surprise. These things could have orbits that are hundreds or thousands of years and so the first time we see one might be the last time we see one because it could be headed for Earth. And so these things could fall into the Solar System and smack right into a planet and you know, cause a lot of destruction. Because they also they move really really fast. They've been accelerating for a long time, falling in towards the Sun, and so they have a huge amount of kinetic energy. This is not a gently tossed snowball. This is like a rocket.
This is like a rocket propelled, missile launched snowball.
Yeah. You give like a really hard block of ice to a major league pitcher and stand right in front of him as he throws it at your face. That's about how terrifying this is.
Just like when they threw those frozen turkeys at airplanes to see if the airplanes would break.
Is that a real experiment you used to make that up.
No, that's the real thing. They shot frozen turkeys at an airplanes to see what would happen. And it's happened before, right, Like, our solar system has gone pelted by giant snowballs, and some of them even hit some planets.
Yeah, exactly. If you think, oh, that's not likely to happen, or it might only happen every thousand or million years, we don't know how often it happens, but we do know that it happened recently. It was in the nineties that a big comet hit Jupiter comet Shoemaker Levy. It broke them into a bunch of pieces, and each one pelted Jupiter, and even after it broke up, it made fireballs that were larger than Earth when each one hit. So these are very dramatic planetary events, not the kind of thing we want to have happened to Earth.
Yeah, yeah, that'd be bad news.
It would be bad.
And now, Daniel, I have a note here in the document you send me here, so I'm trying to figure out it says also space centaurs, and that's it. What does that even mean?
Space centaurs are so much fun. I decided to make it a whole other episode for a few weeks from now. But there is this thing in the Solar System called a space centaur. All seriously, it's a thing. Scientists found the thing and called them space centaurs. But they're not like you might imagine, maybe like you know, asteroids that happened to look like the fusion between man and horse. No, they're just the name that you give small objects between Jupiter and Neptune that sort of cross back and forth between the orbits of these gas giants, the sort of like transitional objects.
So they're like we could call them space unicorns or space griffins. That would be too crazy, but we'll go with space centaurs.
I don't know what kind of bananas they were smoking the day they came up with that name, but it did dickle my sense of humor. But they think that maybe space centaurs also have come from the Orc cloud they've essentially fallen in and then into these more stable orbits somewhere in the outer Solar System.
Well, then I vote we renamed comments to space unicorns.
I second your motion, but I don't think we have any jurisdiction here.
All right, Well, it sounds like comments are pretty cool. They might be coming from the Org cloud, this theoretical cloud out there in space which gave us water, which is a good thing, but which may kill us in the future. And so we're studying this cloud. Now we're studying comments more. What are we doing about it?
Well, we're doing everything we can. It's pretty hard to spot these things, right, They're so small, they're so far away. People have one really fun idea for how to visualize these things, and essentially it's to look for star eclipses, Like if we are surrounded by this huge cloud of these little objects, they're essentially black, they're so far away, they don't reflect enough sunlight, but occasionally they should pass in front of stars, causing these little transitions where the star basically blinks out momentarily. So you can look at all the stars and watch them and wait to see if you see one of these eclipses, and if you do, then you can use that to measure like how many things there are out there, but based on the rate at which you see these things, And if you don't, then you can set a limit and say, well, there can't be that many, other wise I would have seen them.
You're looking at, like how the stars are twinkling, Yeah, because they might be twinkling because of a giant comet hitding towards us.
Yeah, or just a giant, silent frozen comet passing between us and that star. And you know it has to line up just right. You have to draw a line between the Earth and that star super far away, and then the ork cloud object has to basically break that line in order for there to be this eclipse. So it's not that likely, but there are a lot of stars out there and maybe a lot of ork cloud objects, So if you get enough telescope time, you might be able to spot.
And unicorns are pretty magical, so you never know what they're gonna do.
What if they're all turned out to be rainbow colored, that would be amazing race. Yeah, it could also be that if we pass nearby another star, that that star could like pass through our orc cloud, causing like a new bombardment of comets. Wow, And that would be sort of a confirmation because we'd see a lot of these things rushing towards the Inner Solar System.
Well, clearly we need to build an ice for it, Daniel around the Earth. Can we do that?
Yeah? I think it's called Neptune. That's an ice giant, and hopefully it captures these things as they come into the Inner Solar System. You know, we actually do have the gas giants to think for protecting us from a lot of these things. They tend to pull them in and they also tend to clean them up. So without those big planets out there protecting us from the OC bullies throwing snowballs, we would have had a rougher time of it.
Wouldn't it be ironic if there was like a giant commet heading towards us, but then at the last minute, Pluto gets in the way and blocks it.
That sounds like the plot of our movie. That sounds like a good slow motion scene at the end.
And everyone's like, oh, Pluto, we took you for granted, but now you see it's us all.
It's too late, but now we value your contribution.
All right. Well, the next time you look out into the night sky, we hope you think about what's out there and what could possibly be out there, and also think of ice unicorns floating out there in space.
And remember that there's a lot of things out there that we still don't understand, sources of mystery, sources of wonder, and sources of danger. So we better get on it and figure this stuff out before it wipes us out.
Or it might be too late we're ready or not. All right, Well, we hope you enjoyed that. Thanks for joining us, See you next time.
Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact, but the people in the dairy industry are That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digesters to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
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