This video is sponsored by Brilliant dot org. The Star Wars saga currently consists of eight films: The original trilogy, the ones the memes come from, Les Mis in space, and A New Hope 2: Electric Boogaloo. Within these films, we're introduced to 28 planets and moons ranging from the plains of Naboo to the deserts of Tatooine to the lava of Mustafar to the whatever this is of Felucia. A lot of these planets are clearly inspired by biomes on Earth, such as the grasslands of Europe, the Sahara
Desert, and the lava of Hawaii. But scaling up one part of the Earth to a
whole planet doesn't always work within the laws of physics. A lot of the planets that we see in Star Wars could exist in the real universe though, and we
actually have observations of similar planets around other stars a little
closer to home. But yes, some of them are definitely in the realm of science
fiction. That's the voice of Dr. Hannah Wakeford, an exoplanet researcher at the Space Telescope Science Institute. With her knowledge of planetary science, my knowledge of atmospheric physics, and the Star Wars Wikipedia which is called
Wookieepedia because of course it is We can work out which planets in the Star Wars universe could really exist. May the Force be with us. To begin with several planets almost
identical to the Earth having lots of different biomes, polar caps, and a
planetary radius of about 6400km. So Naboo, Takodana, Alderaan,
Cato Neimoidia, and Wobani can definitely exist. Two more planets which
are very similar to the earth are Yavin 4, the location of the rebel base in A
New Hope, and Kashyyyk, the homeworld of the wookiees. But could they exist? C3PO: Don't be so sure. Yavin 4 is a large moon not much smaller than the Earth orbiting the humongous gas
giant Yavin. Yavin is so big that it's either really low density, which would have to be caused by some strong internal heating, or it's on the very edge of what
we would even call a planet. We know that brown dwarfs, which are massive objects that are bigger than planets but not quite massive enough to turn into stars,
can orbit other stars, and we also know that brown dwarfs can host planets. So the existence of the moon in itself isn't impossible. The issue here is that orbiting so close to Yavin would cause humongous amounts of tidal heating. This is the effect of the near side of the moon feeling a greater gravitational
pull to the planet than the far side. In addition to this Yavin has several other
moons which are similar in size to Yavin 4 which would pull on the moon outwards
when nearby. The combination of these two factors would cause major frictional heating of the moon's interior which would cause the moon to be extremely geologically active. This is exactly what we see on Io, the fifth known moon of Jupiter. It has over 400 active volcanoes and is
the most geologically active place in the entire solar system. Yavin 4 isn't shown to have any volcanic activity and though its wiki page suggests that it experienced some in the past this should continue as the effects
of tidal heating will not diminish over time. So Yavin 4 as it is shown in the
movies could not exist so close to such a large planet. Ki-Adi-Mundi: What about the droid attack on the Wookiees? Kashyyyk Wookiees: [roaring] Yes, thank you. Is described as having a perfectly circular orbit, meaning it stays the same constant
distance from its star and also has no axial tilt, the angle between the planet's
rotation and its orbit around the star. These two combined result in the planet having one continuous season as all parts of the planet receive constant solar heating year-round. There are two planets in the solar system which actually exhibit these two characteristics: Mercury has almost no axial tilt and Venus has an almost perfectly circular orbit. So while it's possible that these two characteristics could coincide and
they would indeed produce a lack of seasons this would be very unlikely so
Kashyyyk gets a maybe. several other Chewbacca: [sad grunt] Several other Star Wars planets are also similar to what we see in the solar system Tatooine for example is a combination of
Mars' dry climate with Earth's thicker atmosphere. Jakku, Jedha, and Geonosis are
also very similar, particularly Jakku as it once had water which has since frozen
or been lost which is exactly what we currently think happened on Mars. The interesting thing about Tatooine is that it's in a binary star system: a planet
orbiting two stars which orbit each other. This gives it its famous twin
sunsets. Binary stars are in fact the most numerous, certainly in our galaxy,
and binary stars have been observed to have planets around them - the first
discovered was called Kepler 16b, which much like Tatooine orbited two stars,
one yellow and one red, but you can have many types of binary systems. Tatooine is
likely in what is called a p-type binary orbit where it goes around both of the
stars, but you can also get S type binaries where the planet orbits one of
the stars but not the other. But you would still often see two suns in the sky in both of these configurations. This also applies to another planet with two suns: Endor, the home of the Ewoks. Wicket: Yub Yub. So Tatooine, Jakku, Jedha, Geonosis, and
Endor can all exist. But there's one more planet which is very similar to a planet
in our solar system. Bespin. It's pretty far but I think we can make it. A mining colony? Bespin is a gas giant, about the size of Saturn, where a cloud city floats in a breathable layer of the atmosphere. From the gas giants in our solar system it's very clear that it's not plausible for a breathable stratified layer to exist in the planet's upper atmosphere where cloud city is. If we move the gas giant close enough to star we might be able to get some upper
parts of the atmosphere hot enough that everything would not freeze but that's
just the first challenge. Say we have the right temperature at the right pressure in the atmosphere where human lungs could survive. Next we have to have the material to form breathable air and we have to keep it there. The air we breathe is mostly molecular nitrogen and oxygen If we combine this in the 80/20
ratio of the Earth's atmosphere this would have a mass around 12 times that
of hydrogen and helium which would be making up the majority of the gas in a
gas giant planet. If the atmosphere is then stratified into layers this layer would be much much deeper in the atmosphere (it's much heavier) where the
pressures would be far too high for humans to survive and temperatures would
be much hotter too. So sadly, Bespin doesn't make the cut. Lando: It's not my fault! This still leaves us with plenty of planets though, some of which have parallels in the Earth's past, or in its future. The frozen planet of Hoth, for example, is what the Earth is hypothesized to have looked like several times in its past during periods known
as Snowball Earth. During the last of these hypothesized episodes about 650
million years ago, atmospheric oxygen would have been at a level which was
breathable - so Hoth as it's shown in the films has historical precedent. Mustafar
by contrast is an extremely volcanically active moon which is covered in lava
flows and active volcanoes. This resembles another period in the Earth's history:
the Hadean The Hadean was an epoch about 4 billion years ago when conditions on the Earth were literally hellish. Extremely hot, with molten rocks
covering the surface and the planet being hit by a huge number of meteorites.
The difference between the Hadean Earth and Mustafar, however, is that while
Anakin and Obi-Wan are able to breathe perfectly normally on Mustafar, the
atmosphere of Earth during the Hadean was very dense an almost entirely carbon dioxide, which isn't exactly breathable even to a Jedi. So Mustafar as shown in the movies just
doesn't really make any sense Darth Vader:NOOOOOOOOOO I mean, of all the people of Darth I
thought you'd be happy about that. Felucia is a planet that briefly
features in episode III but is completely distinct from all of the
others, being a multicolored jungle of huge plants. The planet itself is a bit
smaller than the Earth and so has a surface gravity about 75% of the Earth's -
this would help the plants to grow to greater sizes, and apart from the colors
this is pretty similar to Earth during the Cambrian about 500 million years ago.
So assuming the atmosphere of Felucia can mix nutrients and water around the
planet with strong circulation it could exist. Two planets which resemble what
the Earth might look like in the future are Coruscant and Hosnian Prime, both being densely populated planets about the same size as Earth. Coruscant is actually listed on Wookipedia as having a population of 1 trillion beings and
judging by the cities shown in the film this also seems about right for Hosnian Prime. The issue here is that Earth, with a population of just seven billion people, is becoming hotter and hotter due to the buildup of gases like carbon dioxide and methane in its atmosphere. The effect of one trillion people on a similarly sized planet doing similar industries would be absolutely devastating. So either Coruscant and Hosnian Prime are doing some serious geoengineering - not impossible given the technology in Star Wars - or they should be substantially hotter than they are shown to be, so they get a maybe. Obi-Wan: I hate it when he does that A planet with a similar issue is Eadu, which is shown to be covered in dense clouds and storms. Water vapor is actually a tremendously powerful
greenhouse gas, strongly absorbing thermal wavelengths of radiation, so
assuming that Eadu is orbiting a star similar to our own at a similar distance
it should actually be boiling hot. But it of course could be orbiting a weaker
star or further away so it could still exist. Two planets from the newer films
which are very similar are D'Qar and Lah'mu: relatively small, terrestrial planets
which have rings similar to Saturn. We think of rings as being around gas
giants like Saturn and Uranus but it's always been theoretically possible for small terrestrial planets like Earth to maintain a ring system. And recently in October 2017 it was discovered that there's a ring system around the dwarf planet Haumea, which orbits in our solar system just outside of Neptune. So it's been shown to be possible for small
terrestrial planets - even weird tiny elongated ones like Haumea - to have
rings. There are differences between the rings though: D'Qar has rings which are composed of loose rocks, consistent with a disintegrated moon or two: that could definitely exist. Lah'mu on the other hand looks to have rings like Saturn made of tiny ice and dust grains. The ice suggests that the planet formed much further out in the star system than the habitable zone (the range of orbits where liquid water can exist on the surface of a planet) This is kind of possible if the
habitable zone of the star moved over time to allow that planet to then become
habitable, or possibly there's a very strong greenhouse effect on Lah'mu, but
this still would probably impact the composition of the rings that we see. So
it's a tentative maybe for Lah'mu. This leaves seven planets which don't have
direct analogs either in our solar system or in the Earth's past, and... Librarian: If an item does not appear in our records,
it does not exist! Sheesh. However for the past 30 years or so we've observed planets around other
stars or exoplanets some of which are similar to planets in our solar system
but many more are truly weird. There are a number of techniques we use to observe
exoplanets. The first was called radial velocity. This simply measures the pull the
planet has on the starlight over time, causing a Doppler shift in the light as it moved towards us and away from us due to the pull of its planet. But the most prolific method being used
is the transit method. This measures the change in the amount of light seen of a star as the planet passes in front of it and blocks out some of that light. From observations of thousands of exoplanets
in our region of the galaxy alone, we know that the most common type of planets are ones we don't actually see in our own solar system: Ones in between the size of our rocky earth
and the icy giants Uranus and Neptune. One class of planets in Star Wars are the water worlds: Kamino, Ahch'To, and Scarif. These are planets which are almost completely covered in ocean with only small islands jutting above the water. We know that several bodies in the
solar system contain water, including the moons Europa, Enceladus, and Ganymede, but only earth has liquid water on the surface and while we can't directly observe
liquid surface water on exoplanets we can use other measurements as proxies,
like the amount of water vapour in the atmosphere
of an exoplanet. Using these proxies we've discovered several objects which could potentially be ocean planets such as the mini Neptune GJ 1214b.
Observations of GJ 1214b so far suggest that it's a world shrouded in optically thick clouds which
would block out most of the star's light, making the surface, if there is one, very
eerie and dark. So while we don't have direct observations of ocean planets there's nothing in planetary science that says they couldn't exist and we have pretty good evidence that they should. So Kamino, Ahch'to, and Scarif
are quite possible. Lama Su: Magnificent. Another planet which is almost a water world is Dagobah, where Master Yoda makes his home The whole planet is one massive swamp teeming with life, which implies that the planet is almost completely flat, and waterlogged. In fact the Wookieepedia page for Dagobah says that the planet is volcanically dead, with only small remnants of any tectonic
activity remaining, such as the smoothed down
remains of Mount Yoda. Really? Yoda: [laughs] We think of planets as being geologically
active because that's what the Earth is like: constantly shifting and changing
thanks to continental drift and new land being formed by volcanic action. But that
tectonic activity can just stop. Similar to Jakku this is what we think happened on Mars. There are plenty of features such as the huge Valles Marineris and
Olympus Mons which indicate that there was tectonic activity in the past, but as
the planet cooled the molten rock between the tectonic plates solidified
and the planet became volcanically dead. It seems like the same thing happened on
Dagobah so it could exist. This leaves us with three final planets
which are truly weird: Utapau, Mygeeto, and the invitingly named Starkiller base Utapau is a really odd one. It's very similar to Earth in terms of the
composition and size but all the oceans have drained through holes which used to
be magma chambers leaving the planet barren and covered in sinkholes with
subsurface oceans There are a few problems with this. I actually got a friend of mine with a PhD in geology to look at Utapau and he sent me a
very long, angry message about how, quote 'geologically and physically wrong it is' Firstly the water wouldn't be able to drain through holes that used to be magma chambers, because magma chambers either erupt and have the rocks above them collapse, forming a caldera, or as is more likely have their contents
solidify and freeze into very hard rock Secondly even if all the water in the
oceans were to drain subsurface if Utapau is anything like Earth then
temperatures will increase below the surface by about 30 Celsius per
kilometer that you go down So a subsurface ocean would exist either a
steam or a supercritical fluid and because either would be less dense than
the surrounding rock it would rise to the surface as geysers or other
geothermal activity Which would make for a really cool planet but not what we're
shown in the films So in short there are a number of
problems with Utapau Tion Medon: Thousands Next, Mygeeto is a freezing planet similar to Hoth but the interior has completely cooled and left the planet volcanically dead The surface is covered with
huge crystals of all different kinds We've already seen with Hoth and Dagobah that planets can be extremely cold and can be geologically inactive, so those features on Mygeeto are fine The massive crystals are one of those cases where we might have to allow artistic license We know that huge crystals can form
on Earth under the right conditions such as the cave of crystals in Mexico So given exactly the right set of conditions
Mygeeto could probably exist Then lastly we have Starkiller base: a planet that was hollowed out and turned into a weapon that keeps the power of a star inside itself In terms of the laws of physics... Han Solo: that's not how the force works Chewbacca: [I'm cold] I think we just have to give them some creative license with that one So of the 28 planets and moons,
we reckon that only five couldn't exist in the real world,
with some big uncertainties on some of the others But none of the worlds in
Star Wars come even close to real planets we've seen around other stars Out of the thousands of exoplanets that
have been discovered none surprised people like the
planets we now called hot Jupiters They're gas giants the size of Jupiter that orbit their stars closer than mercury does to the Sun and almost all orbiting in under five days These giant planets are so close to their
stars that they're often hotter than you would be sitting under a
rocket as it took off and that does funky things to an atmosphere One such hot Jupiter has high speed winds whipping around over 5000 miles an hour
with cloud droplets made of molten glass Another has clouds that are likely formed
at the same substance that makes up rubies and sapphires here on Earth But it's not just the giant planets that have surprised us The planetary system around the star Trappist-1
has seven earth sized planets orbiting it in such
a tight configuration that if life were to exist there and reached our level of
technology, planet hopping would be an easy holiday destination So while science fiction might be strange, it's got a long way to go before it becomes
even stranger than science fact Thank you for watching this video!
In making it Dr. Wakeford and I have made use of very real science to tackle
science fiction including tools from astrophysics, atmospheric physics, and the
study of exoplanets Now that I've submitted my thesis I have more time to make science videos like this one which is hopefully piqued your interest in the
science of planets and of atmospheres But if you really want to understand
those concepts the only way to do that is to tackle some problems yourself During my PhD I found that I didn't understand the topic fully until I'd
actually tried it myself and done some problems If you'd like to support science videos
on this channel then go to Brilliant.org/SimonClark
(and I'll put that down in the description) where you can sign up for
brilliant for free, and in addition to that the first 200 people to use that link
will get 20% off their annual premium subscription Huge thanks to Dr. Wakeford for
agreeing to be in this video If you'd like to check out her research
or the card game about female scientists through history which we made together then check the links in the description Sheev: Do it. Thanks also must go to my friends Tom Dowling,
and newly Dr. David Arnold for their help with the script As well as checking out Brilliant.org/SimonClark if you'd like to learn more about the
science of ice on Earth and indeed other planets
then check out the link on the screen and in the description to the Crash Course which
Dr. Dowling and I are currently making on this channel Lastly though thank you again for watching If you enjoyed the video please do give it
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Correct me if I'm wrong, but if Dagobah has no tectonic activity, wouldn't it lose it's magnetic field, then have it's atmosphere stripped away like mars?
This was made by me with help from me geology and astrophysics friends! If you have any questions please do free to ask here :)
My problem with Star Was planets has always been the poles. I mean, even Mars has ice caps. Not to mention axial tilt or orbital path.
The idea that an entire planet would be one biome has always rubbed me the wrong way--maybe these planets could exist, but not in the monolithic way that they've been portrayed.
As good as this video is, I'd like to see a biologist or meteorologist pitch in on it, too.
Absolutely. The different variations of planets in our universe is almost infinite. K and G-type stars are the moneymakers with countless habitable planets.