Why the Earth exists because of Saturn | Migration of Planets

now one thing you might not know is that the positions the planets in the solar system are in today haven't always been that way so the place that a planet formed isn't necessarily the place it ended up just due to the complicated interactions of gravity between all the planets comets asteroids and bits of rubble left in the solar system and it turns out that it's my favorite planet saturn that made the difference between earth ending up in the nice goldilocks zone around the sun where it's not too hot and not too cold for life to start you know where we are now or being flung out into the icy cold depths of interstellar space so to understand why this is and to understand this whatever it is 389th reason why saturn is my favorite planet in the solar system we have to understand how the solar system formed and you might be wondering well how in the universe did we even figure that out and it came from sort of a combination of a couple of different things the first is just observing the solar system like noticing where we find certain types of objects like asteroids and where we find certain types of planets in the solar system too the second is from looking at other star systems in the milky way so that's looking at other planets orbiting around other stars in our galaxy and the third is by running computer simulations or simulations of all of these interactions due to gravity of lots of planets forming around a star so when we observe newly formed stars in the milky way we see them shrouded in sort of lots of dust and gas and usually that starts out life is sort of a sphere around the star but the star when it starts to form is spinning and so just like when you take a ball of pizza dough and you throw it up above your head and set it spinning and it flattens out into a flat disc the same thing happens around a star and all that material condenses into a flat disc and that's why the solar system all the planets are in sort of that same plane because they reformed from this disc and they formed from the debris that can be anywhere from sort of like nanometer sized trunks to sort of centimeter-sized chunks they get attracted to each other by gravity and over time very slowly clumped together to give you what we call a planetesimal which is usually sort of like kilometer-sized chunks of rock kind of like you know asteroids and comets and stuff that we see in the solar system from these planetesimals in computer simulations we see a runaway buildup under gravity into fully formed planets now close into the star there's just less material there right because there's just less volume of space for you actually to put that material in so the planets that form close into stars tend to be a lot smaller because there is less material there for them to form out of they also though tend to be formed of heavier elements of metals like carbon and iron for example because those elements have sunk towards the center of the system under gravity further out though there's a lot more material so planets can grow a lot bigger and we find that when they start to hit about 10 times the mass of the earth they become heavy enough to start actually attracting the hydrogen and helium gas that's still available in this sort of like disc of rubble around the star the gas that really didn't go into forming the star they start to attract that and that gas if it's cold enough can condense onto the planet i it can form this like atmosphere usually very very thick atmospheres of this gas to give us things like the gas giants of jupiter satin uranus and neptune and so that really nicely explains sort of what we see in the solar system right where we have the smaller rocky planets of mercury venus earth and mars close into the sun and then we have the much much bigger gas giants of jupiter saturn uranus and neptune much further out so that was sort of the agreed upon scientific explanation for how the solar system had formed for many many years but it wasn't really until we started observing other planets around other stars in our galaxy that we realized that that story just didn't add up anymore and it was because of these very strange planets that we were observing that we realized this so anything from rogue planets planets that aren't orbiting a star at all they're just freely floating through interstellar space or to planets that don't all orbit in the same plane in one system you know you might have one planet that's orbiting the pole of the star and the other planet is orbiting so around the equator and it's just this big chaotic mess or you've got planets that are on huge oval shaped orbits that take millennia to orbit their star there's these huge elongated things kind of like what we see the orbits of comets in our own solar system but the biggest challenge to this idea was hot jupiters so the majority of planets that we detect around other stars are hot jupiters i.e they are jupiter-sized or bigger but they orbit so close to their stars they're sometimes even sort of within the distance that mercury is to the sun around their star that doesn't make sense under the sort of the idea of how we think the solar system formed because it's far too hot there for the gas to condense onto the planets and make those huge big gas atmospheres like what we see with the gas giants out in our solar system but also there's just not enough material around the star to make a planet that big very close in and so the idea that's been proposed to explain these hot jupiters and lots of other things that we see in in star systems that we observe that was sort of proposed in 2005 and has slowly become accepted sort of theory by the sort of science community of researchers who work on this is the idea of planetary migration the idea that where a planet forms is not necessarily where a planet ends up so it's very likely that these hot jupiters actually did form quite far out from their star but then if migrated inwards to be very close to them i guess the remaining question though is why has that happened well one idea is that as these star systems form and you start building up these planetesimals of sort of kilometer-sized chunks of rock and material star systems look a bit more like the asteroid belt in the solar system rather than sort of having these very sort of like separated out planets and if you have a system that looks like that then there's going to be a lot more interactions between two objects as they either collide which we think is how they build up their mass or maybe even just fly by each other now in those kind of flybys the two objects actually exchange energy and how much energy you know is exchanged from one to the other really depends on how big the objects are so the smaller objects in that sort of flyby and exchange usually gain energy we usually often use this as sort of what we call a gravitational slingshot if we're trying to send a probe out to the far reach of the solar system we can sort of slingshot around mars and it can gain some energy to get it way out to the edges of the solar system the same thing can happen if sort of two lumps of rock meet each other as well right so the smaller object gains energy and that means it can actually be slingshotted out of the system entirely perhaps causing these rogue planets or perhaps putting the object on these really really long elongated oval shaped orbits around the sun the same sort of kind of orbits that the comets have that take you know millennia to go around but what also happens in those interactions is that the larger object loses energy and so if the larger object loses energy what then happens is that it starts to sort of sink towards the center because of gravity you've got the much larger star then pulling on it more as it loses energy now when this model of planetary migration was first proposed back in 2005 you know its main idea was to explain the hot jupiters that we were seeing but people quickly realized that if this had happened so often in other star systems in our galaxy then surely it must also have happened in our own solar system as well and so this is where sort of the computer simulations come into it and so if we try and match what we see today with lots of different initial conditions and what could have happened in the solar system we build up this picture of what is the most likely thing that has happened according to sort of our simulations that take all the laws of physics and what we find is that first of all all the gas giants probably formed first before sort of the terrestrial planets of mercury venus earth and mars and yes they did indeed migrate inwards and that migration inwards saw them encountering so many sort of random bits of rock and rubble on their way in this is probably what's caused you know the comets to be on such elongated orbits around the sun but also those interactions probably ejected a load of those objects from the solar system as well you know a huge number of them who knows how many of them you know since that happened maybe four billion years ago have actually encountered you know another star in their lifetimes now and in the same way that we had the interstellar visitor umura back in 2017 that we think was one of these sort of ejected objects from a newly formed star system at some point but the simulations also show that jupiter probably migrated in to about the distance that mars is from the sun today if it did that it would have cleared out a lot of those planetesimals from the area so that probably explains why mars is so small for its position in the solar system so venus and earth are roughly about the same size and mass but mars is probably about half the size and only 15 of the mass of venus and earth probably because all those planetesimals that it could have used to grow much bigger were thrown out onto much more elongated orbits or even out of the solar system entirely by jupiter it also explains why the asteroid belt is where it is between mars and jupiter because if jupiter crossed this region you know it has such a strong influence on the gravity of that region that it will probably have stopped all of those planetesimals called asteroids today from clumping together to form a new planet but obviously the big question is still why didn't jupiter go any further and why now has it been pulled back to the position that it's in today and you might be wondering well why do we care and the reason that we care is because if it had gone any further it would have definitely disrupted earth's development into a planet and maybe even thrown out all of the proto-earth material into interstellar space just killing all chances that life would develop on it now as you probably guessed the reason for this and the reason that we are all here today me making this video you watching this video is because of saturn let's look at it again oh it just never gets old it's just so gorgeous so as jupiter and saturn both migrated inwards at the same time in towards the sun they ended up in what's called a resonance about when jupiter hit that orbit of mars it was a two to one resonance to be precise and what that means is that for every two orbits around the sun that jupiter makes saturn makes one orbit it's a very stable sort of position for those planets to be in the gravitational forces are really nicely balanced it's very difficult to break that resonance once they're in it we see this actually when we look at a lot of other star systems of planets as well you know we see them in resonances and it's quite cool actually because if you get a system where all the planets are in resonance you know like a two to one a three to one five and a seven to one sort of resonance all on a chain on the way out you can sort of make each planet sort of play like a note every time it goes around once around the star and then sort of again when they sort of all line up and resonate together they play the notes together and it makes this really interesting music that's sort of made out of nature which i absolutely love like listen to the to this system [Applause] so saturn essentially sort of held on to the reigns of jupiter and stopped it going beyond the orbit of mars because of this resonance but as i said these resonances are very hard to break and yet we know that jupiter is no longer sort of at the orbit of mars it's much further out and jupiter and saturn are no longer in a resonance so what we think eventually broke that resonance was then the interaction with the uranus and neptune also migrating inwards as well this sort of added interaction due to gravity combined with sort of breaking that resonance forced jupiter and saturn's orbits to become much more oval-shaped and circular it pushed all of the planets back out again far away from the sun where they also interacted with all the sort of icy bits of rock and planetesimals left at the outside of the solar system pushed them way out into what we call the kuiper belt today way past neptune and eventually the gas giant sort of settled back down into those roughly circular orbits that we see them in today now although this model reveals a lot about our own solar system and explains a lot of the things that we've seen in other planetary systems in our milky way galaxy there's still a couple of things it's not quite been able to explain yet and one of those is you know why more star systems aren't in resonance with each other if these resonances are so stable you know when planets reach them it's very difficult to break if they've been migrating all over the place and so is it just that there are other planets in these systems maybe that we haven't spotted yet with our methods of detecting planets that will have interacted with them to break these degeneracies or is it something else entirely the big question for me is why these hot jupiters stopped migrating inwards where they stopped right in sort of that mercury sort of distance-ish from the sun like what stopped them from just spiraling in and being completely destroyed by their star right maybe it's just that we're actually seeing a snapshot of this sort of migration inwards right and we're seeing it at a specific point and if we watched for long enough for centuries or millennium whatever it would be we would eventually see these planets sort of get consumed by their star or maybe there's some reason that they did get halted there maybe again it's something to do with sort of these complex interactions due to gravity between all of the objects in these systems that somehow halted them right in close to their star i mean like most things in astronomy and astrophysics it's you know more data is needed more time is needed to observe them as always and that will come with we've got the launch of the tess telescope that's gone up in the past year or so that's the follow-up of the kepler space telescope which is about 4 000 planets plus we're detected with kepler it's one of the most successful missions ever then you've also got the launch of the james webb space telescope in 2021 next to your fingers crossed and the exoplanet community are very excited for that because that's going to help them characterize the atmospheres of these planets that they're looking at and perhaps sort of probe you know what's in these big hot jupiter atmospheres is it similar to the solar system or not i'm very excited to see what will come out of all of these sort of observations and missions that are planned for the future and what we will be able to learn maybe about the origins of our own solar system and origins of our own planet here on earth too and perhaps maybe just maybe we'll learn one more reason that i can add to my ever-growing list of why satin is my favorite planet before we get to everybody's favorite part the bloopers i just want to say a big thank you to this week's video sponsor which is brilliant brilliant is a website with courses on all areas of science and maths and the courses are fun they're interactive and most importantly they get you to learn by doing so they break down a very complex topic into chunks that are easy to understand and easy to remember now brilliant have a big astronomy course collection too including courses on star formation from you know these gas and dust disks that we spoke about in this video to the different methods that we use to find exoplanets planets not around our sun but around other stars in our galaxy the milky way these courses are so great because they don't just teach you about planets but also about how telescopes work you know going through their limitations so you can work out what is the smallest thing that these telescopes can see and therefore what exoplanets can we spot if you like the sound of that and you want to support me and my channel then head over to brilliant.org forward slash dr becky that's d-r-b-e-c-k-y and sign up for free plus the first 200 people that go to that link will also get 20 off their annual premium subscription so go forth and learn something with brilliant thank you very much brilliant for sponsoring this video and now those bloopers oh it's that time again though isn't it like just i just place your bets now people on how many comments there's gonna be on how i pronounce saturn like yes grammar police i know there's a t in the middle of it but it's my accent but it wasn't until we started observing other stars in our but the models all show all show show i'm an alien i'm a legal alien i'm a jupiter in real close

Channel: Dr. Becky

Views: 185,467

Rating: 4.8899283 out of 5

Keywords:

Id: cPouwOKMS2s

Length: 18min 31sec (1111 seconds)

Published: Thu Sep 10 2020

Reddit Comments

[u/Haploid-life]

This is absolutely fascinating. She's easy to listen to and you can tell how passionate she is about it.

[u/RadBadTad]

I'm always interested in how sure people are that the current model and current knowledge is the "right" one, even though all the others have been wrong, and the current one can't answer all the questions either. I wish more presenters would say "This is the best we know right now" rather than "now we know" and that sort of thing. Regardless, it's really interesting science!

And I'm having a very fun time saying "hot Jupiter" over and over.

[u/fizzanzith]

It's a nice video and doesn't take to be super advanced in this field to understand what she's talking about. BUT that title with no punctuation a little irritates me, sorry..