The Scientific Implausibility of Starkiller Base

This post contains spoilers for Star Wars: The Force Awakens. These spoilers won’t affect you if you haven’t seen the movie; they’re equivalent to saying, “in A New Hope there’s a moon sized battle station with a superlaser” and “someone gets a hand amputated with a lightsaber in a Star Wars movie”


A lot has happened in the Star Wars universe since the battle of Endor. The Empire is in ruins, and Yavin 5 and the forest moon of Endor both have new planetary ring systems. The Rebellion has given way to a new Galactic Republic, but there is a spectre of evil looming in the unknown areas of the galaxy: the First Order, a malevolent force that has built a planet-sized superweapon capable of destroying entire planetary systems from across the galaxy. The Starkiller gets its energy from harvesting entire suns, moving from one solar system to another to feed this massive weapon of terror.

We’ve had nearly forty years to argue the plausibility of the Death Star, lightsabers, parsecs as a unit of time, and hyperdrives. It’s time to pass the hallowed tradition of arguing over fictional spacecraft to a new generation. Starkiller Base is a cool idea, but does the science behind it hold up? No. It’s completely implausible. It makes for a great story, but it’s completely implausible.

Aren’t you a little short for a stormtrooper installation?

In The Force Awakens, we’re given a direct visual comparison between the Death Star and Starkiller Base. The diameter of the Death Star is known (120km), and with this we can make a pretty good guess of the diameter of Starkiller Base. From what is seen in The Force Awakens, I’m going to say Starkiller base is about ten times the size of the Death Star, or about 1200km diameter.

1200km is actually fairly small for a planet, but is it too small? If we’re to define a planet the same was the International Astronomical Union (IAU) does, we have only a few things to consider. According to the IAU, a celestial body is a planet if it orbits the sun (an invalid qualification, this is in a galaxy far, far away), if the celestial body has cleared its orbit of debris (like a star, for example), and if the planetary body has reached hydrostatic equilibrium; basically, if it’s a sphere or not.

If we were to compare Starkiller Base to objects in our solar system, we would find a few similar objects. Starkiller Base is a bit larger than Ceres, the largest object in the asteroid belt. Ceres is large enough to pull itself into a sphere, so we can only imagine whatever planet the First Order hollowed out would have as well.

StarWarsTech 01

While the physical dimensions of Starkiller Base makes sense, the gravity doesn’t. The existence of a thick atmosphere doesn’t. Being able to suck down a star doesn’t. It’s just a movie, though, and by defining the dimensions of Starkiller Base, we can get to far more interesting calculations.

Kylo Ren Under Pressure

The Starkiller is a planet after all, and with that comes everything that comes with planetary-sized bodies. This means geology, hydrology, possibly tectonic movement, and yes, an atmosphere. While most of the surface of the planet of Starkiller Base was left alone for the construction of a star destroying superweapon, the Starkiller Base does have one very unique feature: a huge gash along the planet’s equator larger than any possible natural geological phenomenon.

Starkiller Base, as seen in The Force Awakens poster
Starkiller Base, as seen in a The Force Awakens poster

If we assume the planet that would become Starkiller Base was reasonably Earth like, with similar gravity, atmosphere, but only 1/10th the diameter, we can gain some insight into what the inside of this base is actually like. Given an atmospheric pressure of 1 atm at ‘sea level’ (or whatever altitude the Starkiller surface scenes take place at), and assuming the weapon canyon’s depth is approximately one fifth of the radius of the planet (a good guess), we can calculate the atmospheric pressure a the bottom of the weapons canyon.

Doing the math for a weapons trench that is about 240km deep, a temperature of 0°C, and Earth-like atmospheric pressure and gravity on the Starkiller’s surface, we find the pressure at the bottom of the weapons trench is an astonishing: thousands of atmospheres of pressure. It’s a product of the exponential nature of the barometric formula, and save for force fields and gravity plating, there’s no way around it.

To put this in perspective, the pressure at the bottom of the Pacific ocean – Challenger Deep in the Marianas trench – is about 1,000 atmospheres. The First Order stormtroopers wouldn’t really be breathing the air this far towards the planet’s core, they would be swimming in the air.

At these temperatures and pressures, water turns to a phase of ice not normally seen on Earth – phase VII ice. Air turns to liquid, too: these pressures are above the liquid-vapor transition line of nitrogen and oxygen. Even if the First Order was able to keep the atmosphere at a balmy 0°C at the bottom of the Starkiller’s weapons trench, the interior of this planet-sized megaweapon would still be uninhabitable.

The Starkiller and E=mc²

The Starkiller does exactly what it says on the tin: it sucks up stars to run a single, huge, system-destroying megaweapon. Everything in the universe and extended universe is conserved, and we’re left with the question, where does the star actually go?

First, we can assume the star hoovered up by the Starkiller is converted directly into energy; if it were not, the Starkiller would also gain the mass and the gravity of the star it kills. There are obvious problems with an occupied planet with the mass of a star, and we don’t see the gravity of Starkiller base change on-screen, anyway.

If the star used to power the Starkiller is converted directly into energy via mass-energy equivalence or E=mc², we can get a good idea of the power output of this weapon. Additionally, we can calculate what would happen if the process of converting mass to energy isn’t exactly 100% efficient.

Again, we’re left to make a few assumptions about how the Starkiller actually works, but we do know from The Force Awakens that the Starkiller travels from star to star, consuming it entirely, and turning that energy into a focused energy beam that destroys entire planets. The size of a main sequence star can be approximated by its color, with stars larger than our sun being bluer, and smaller stars having a reddish tint. From what The Force Awakens, we can make an educated guess that the star in the final act was smaller than our sun, perhaps a K-type star of around 0.15 solar masses.

Directly converting that mass into energy yields an astonishing number: about 1.5 x 1031 Joules of energy. This is more than enough energy to wipe several planets off of a galactic map. This is nearly equivalent to all the energy released by our sun over the course of one thousand years. It’s a mind-boggling amount of energy, but if you need to blow up planets from across the galaxy, it’ll do the trick.

Starkiller Base will have to contain all of the energy from a star in some sort of massive, planet-sized battery. Most of the energy from the star will go into this energy beam, but not all of it; nothing is 100% efficient after all. Assuming for a second that Starkiller Base is 99.999 percent efficient at converting the mass of a star into a system-killing beam, that still means 1.5 x 1027 Joules of energy emitted as waste heat. That’s the equivalent of 350 quadrillion tons of TNT, or thirty trillion Little Boy-sized nuclear bombs. This is just the waste heat from Starkiller Base, and not the output of the energy beam itself. By any measure, Starkiller Base has an incredible cooling system.

But what exactly happens to this waste heat? Since The Force Awakens doesn’t show any radiators sticking up out of the atmosphere, so all of this energy must go into the atmosphere. What happens when all this energy is dumped into the atmosphere is a simple first year physics or chemistry problem.

The relationship between an amount of energy and a rise in temperature is given in every physics and chemistry textbook as Q = cpmΔT, where Q is the amount of energy, cp is the specific heat of the atmosphere, m is the mass of the atmosphere, and ΔT is the change in temperature. We can assume a value of 1.0 kJ/kg for the specific heat of the Starkiller’s atmosphere, and an atmosphere with a mass that is about 1/10 that of Earth’s (5×1018 kilograms), we come up with a shocking number. The waste heat from the Starkiller’s stellar mass to energy conversion is enough to raise the temperature of the atmosphere of the First Order’s megaweapon to nearly 300 million degrees. This is the problem with turning matter into energy: you get a lot of energy. If the mass to energy conversion process of the Starkiller is just the tiniest bit inefficient, it’s enough to vaporize everything on the surface.

Does it matter?

Is the megaweapon in A Force Awakens plausible? No, but that’s really not the point. It’s just a movie, after all – and a great one at that – with starships maneuvering in space just like they would in an atmosphere, beams of light that magically stop in mid-air, and an energy field that surrounds and penetrates living beings and binds the galaxy together. These things aren’t real, and putting real numbers behind them misses the point entirely. It is, after all, just a movie, but putting the numbers behind a great story can be just as fun.

112 thoughts on “The Scientific Implausibility of Starkiller Base

  1. I was just talking to a coworker about this yesterday, with the assumption that the mass of the star was stored within a planet. I was running on an assumption that the base was roughly the size of Mars. However, the 1200km diameter figure makes things more interesting.

    If it held the entire mass of the sun, that would put surface gravity at 37.6 million g’s. Wolfram helpfully tells me that is 20% of the acceleration a proton experiences in the LHC. This gives an escape velocity of 21000km/s, which is 7% of the speed of light. Unfortunately, this is low enough where fun relativistic effects don’t happen.

    1. Well, we know what happens when you compress the mass of the Sun into something planet-sized, because those things already happen. They’re white dwarfs. The entire atmosphere would begin fusing.

  2. Couple things:

    1. Converting the star’s matter to energy won’t actually alleviate the effects of gravity. As far as spacetime curvature is concerned, mass and energy are the same thing. There’s still exactly the same amount of mass-energy there, if anything it’s just denser, so there should be gravitational changes, either as the mass-energy is absorbed and stored, or even if it just passes through in huge streams. I guess here’s where we need some quick technobabble about storing it in hyperspace or something…

    2. Apropos of last week’s post, this seems to weigh in favor of the Death Star(s) having been a relatively minor expense for the Empire. A fragment of the Empire being able to build a weapon hundreds of times larger, despite operating on the fringes of its former territory with, presumably, a fraction of the Empire’s former resources (and credit score) doesn’t really jibe with the DS being crippling expensive.

    1. Eh….

      It’s actually worse than you think it is. Spacetime definitely knows the difference between mass and energy. A lot. That’s how cosmologists can figure out how much “matter-like” stuff and “energy-like” stuff there was from the CMB. They curve space differently – general relativity says that spacetime curvature is proportional to the stress-energy tensor. And mass and energy don’t have equivalent tensor components.

      For instance, if you store all the energy in photons (some ludicrous EM field which is totally impossible), the time-time component would be a lot like mass: T00 is just density for mass, and T00 is the energy density of the EM field.

      But the other elements aren’t identical, because the equation of state for radiation and for matter are different. For matter, the other elements are all diagonal, and just the pressure. For photons (an EM field), *all* the elements are non-zero. Energy mucks with space much weirder than mass does.

      1. Right. And tensors and stress energy are a bit over my head. Wouldn’t some sort of conservation law still apply though?

        I mean, if I had a magic device that could twiddle the contents of a given fixed volume back and forth between, say, iron and photons, the total energy/mass/momentum will all be conserved. So it would be weird if the shape/size/strength/other characteristics of the resulting gravitational field changed, right? Or maybe not?

        (Obviously mass and energy are normally very distinguishable, and behave very differently, but this seems like a weird situation because you have photons – or whatever form your “energy” is stored in – confined into one impossibly small space.)

        1. No, it wouldn’t be weird at all! Yes, the resulting gravitational field would change. Definitely. Because *how* the resulting energy and momentum are distributed would be changing radically.

          It has to do with how the fields transform. If you’ve got matter, then you can define a comoving frame, and all the matter is doing is just sitting there. Wouldn’t be doing anything at all. No asymmetry in any spacetime direction. Just frozen. And that’s what the effect on gravity looks like – it’s just a point divergence in the curvature, just like the point charge in an electric field.

          If you’ve got *energy*, though, it’s not “just sitting there.” I can’t make a photon sit still. There’s literally *no way* to make a stress-energy tensor for an EM field that’s “mass-like.” So the effect on gravity wouldn’t look like that at all.

          This is why, for instance, a black hole is much different than a black hole with charge (and still different from a black hole with charge and spin).

          1. Weird.

            Any idea what it be like in practice? I mean, we all more or less know what standing on a ball of iron feels like. Are we talking about a different downward force if you’re standing on a ball of photons? Different kinds of time distortions?

          2. Well, kindof. Mass only affects the diagonal elements, so it’s basically like you’re stretching spacetime, which is what makes rays bend towards the mass (much like Snell’s law, which is unsurprising since they both come from Fermat’s principle). The EM field tensor affects the off-diagonal elements, so it’s almost like you’re *twisting* it in addition to stretching it, but that specifically depends on how the tensor is arranged.

            In practice, though, it depends what you mean. Adding energy stored in the EM field tensor is essentially making the geometry of a Reissner-Nordstrom or Kerr-Newman black hole. But if you store *too much* energy, relative to the mass present, Bad Things happen (a singularity without an event horizon forms), which is most likely just a proxy for “our current theories suck for describing crazy crap.”

          3. Also, another interesting point: there’s no such thing as a “ball of photons.” Photons travel at the speed of light. You can’t make them stop and store them in something. You can confine electromagnetic energy in all sorts of various methods, but all of those methods require matter, and all of those methods will generate weird distortions when you get the energy density high enough.

            The idea of “slowing down photons” or “trapping photons” in a medium requires a medium, which means there has to be matter present. So for some amount of energy trapped at a specific spot (not necessarily static), you really have to have mass present. Can’t hold down photons.

    2. Well, you’ve got a story who’s inhabitants have mastered manipulating gravity and hyperspace so well, cobbled together ‘pieces of junk’ and otherwise work well and works well enough that even though it isn’t maintained to glistening perfection -AT-ALL-, it still works. And that lack of entropy or it’s stark minimization of it, is something that is fantastically advanced in of itself.

      Throwing in the ability to play with hyperspace throws out any argument about maintaining the law of conversation when you can transfer matter and energy OUT of the space-time frame your talking about.

      Whatever mass Starkiller base may/may not have, it’s certainly plausible that the builders set up gravity systems to normalize their working environment where they need to like they do on every ship in the fleets – heck i would. We may talk about going to Mars, but I don’t want to live in .33G. I want my 1G so my body keeps up it’s strength. So, even talking about the temperature and pressure of the environment at the bottom of the Starkiller trench is impossible to talk about, without a full explanation of how it was built in the first place.

      Those three things alone, mastery of gravity, hyperspace and minimal entropy (without blunt force trama) make for a really cool world

      1. You beat me to it! They actually specifically say in discussion at the rebel base that the star killer is based on hyperdrive technology. So the answer to all these problems is that the star matter is stored in hyper space (whatever that means!). However, it comes back from hyperspace when the planet explodes, because a star is formed when they all leg it. Presumably that means there’s some sort of conservation law with hyperspace too: what goes hyper must come hither. ( I just made up hither-space as an antonym of hyperspace)…

      2. Mars has circa 0,38g 8sometimes stated to be 0,37), not 0,33g. Also, the energy would have to cross thousands of light years in a short amount of time and the light of the shots go ahead of them.

    1. Ditto. But after 30 years from RotJ, they had X-Wings that were of slightly different design (the engine inlet were half circle rather than full in original trilogy). It is possible the original B-Wing were obsolete and no one made newer versions.

      Then again, they could have been stored on different planet and wasn’t reachable in the short time they had chasing down lost plan across a couple planets (and reuniting Han and Leia in the process) and the hurried plan of attack before the resistance base was destroyed.

      1. The Resistance seemed to have limited resources so they may have just opted for the best all around fighter instead of going with specialized A, B, and Y wing fighters. Just another possibility.

        I look forward to the Republic Fleet going into full retaliation in the coming movies. Assuming the fleet didn’t scatter when the entire government was taken out suddenly.

      2. Apparently, according to some of the new books, the Resistance is using X-Wings that are 30 years old in TFA. This is supported by the fact that the crashed X-Wing Rey drives past on Jakku already has the design sen in the film, and it must be 30 years old because the Battle of Jakku happened one year after Endor.

    1. Yeah it can. Because it’s a movie, not a documentary. And because it’s more Fantasy than it is Science Fiction.

      Plus, our knowledge of physics is not by any means “fact” or set in stone. It is what makes the most sense so far. As it is, we really only have a rough idea of what gravity really is, or how it works. We can calculate it, sure, but we don’t really understand it as well as most people think we do.

      1. I’m not letting you get away with that because whatever physics even an imaginary universe has, it still has to be universal to that universe. So if the behaviour of 99% of that universe is the same as our universe you can’t have something that obviously breaks the rules, nor can you have rules that allow for certain phenomena and ignore the implications of having such things possible, i.e. What those made-up rules would also allow that would totally spoil the feasibility of the plot line.

        Here is a classic example, if I can open up a hyperspace tunnel to send a beam of photons I could just open one end of the tunnel over the jet of a quasar etc. But then my opponent could open another tunnel in front of my beam and the other end behind my back so I would just destroy myself instead of them. I could list many other similar scenarios, but I am sure you get the idea, imagine what you could do with black holes and hyperspace tunnels…

        The problem is, and why these arguments arise, is that people don’t recognise that Star Wars is not science fiction, it is a form of mythology as described by Campbell. http://www.movieoutline.com/articles/the-hero-journey-mythic-structure-of-joseph-campbell-monomyth.html

        1. What is technically feasible is not what is practically feasible.

          In order for your proposed counter attack to happen the defending side would not only need the exact technology in place and functional as you describe it but they would have to know with astronomical precision the location and timingnof the attack.

          While the attacker in this case would have every opportunity to make pre iced coordinates for many potential targets taking countless variables into consideration to be sure the weapon didn’t simply miss by some minute fraction the targets response would be hurried and lacking information.

          1. And I have already pointed out that gravity wave detectors would detect the conversion of the fuel star’s mass to energy as the device was powered up. Relativity limits how fast so much mass could be moved or converted (in a way they are the same thing) in a given time therefore there would be a significant time period for detecting the device “warming up”. blah blah blah etc…. So, give up the “but but but…” stuff because it is a bullshit universe with made up rules so there is no alpha argument that proves one thing over another, and that is that actual point I am making. Get it now? No, OK. So you want to pretend that Star War is science fiction and not a mythology? Then do what I said in the other post an try and get your head around what happens if there is any sized hyperspace tunnel connecting a black hole to any other part of the universe. Seriously go ahead, and earn yourself a Nobel Prize because it is a paradoxical situation that suggests Einstein was not 100% correct and that wormholes can’t exist in the same way that travelling back in time is not possible, it sets up paradoxes.

  3. I loved reading this, but wanted to chime in with a comment… I could be wrong, but I got the feeling from the movie that the weapon did not completely annihilate the nearby star every time it was used. As I understood it, the weapon might get many firings before the star was used up. I also didn’t get the feeling that it was necessarily portable, and that it might be constructed in place, and mostly abandoned when the nearby star was depleted, with the First Order moving on to build a new Starkiller in a new system.

    But yeah, it’s a movie, it doesn’t necessarily have to work, and thanks again for the thought-provoking post!

    1. Seems rather inefficient to abandon after just a few firing. Building a new laser system of that scale probably took many years, and I doubt they could afford to be without the super weapon for so long. They probably have a way of moving the entire Starkiller base to a new star when needed.

      There’s a current “Disney sanctioned” map of the galaxy and it had “Starkiller Base Origin Point” on the map which strongly suggested the base was meant to be moved.

      1. How many times would such a weapon need to be fired? Like the Death Star and our own nuclear arms I imagine it to be more of a deterrent.

        Certainly it would be used to deliver some devastating blows to a stubborn enemy, but it’s not like they would benefit from wholesale destruction of every possible world housing enemies.

        If the weapon were left intact at the end of the movie I could see the destruction of the Capitol as both a tactical strike and a demoralizing demonstration of power. If it were still a threat it’s likely that the resistance would have been left fractured and without the support of other worlds, effectively neutering them and leaving them with so little ground to go to that a planet killer super weapon would be less useful for actual combat than for maintaining authority.

  4. If you suck up a star, why do you need to fire a super-laser? Destroying a planet’s star will effectively kill everyone on the planet. Not as dramatically or quickly, it’s true.

    Of course, after sucking up a star, you need to do *something* with all that energy. Two words: Tesla Powerwalls. :-)

    1. If I remember correctly the target planets need not be in the same system, the weapon could be fired across hyperspace or something. Otherwise a society of the level of those in Star Wars would probably notice the sudden presence of a 1200km wide body near your sun, sucking it down.

  5. The inhabitants of that faraway galaxy have both gravity repulsors and gravity generators. Combined with FTL drives, it would not be unreasonable to assume an expansive control over mass-energy conversion and any relativistic effects from the distortion of space-time. And this even assumes the math in their universe coincides with our own, which it cannot be, since their basic unit of time seems to be the parsec.

    1. Additionally, they’ve got all this hyperspace wizardry.

      My take was that the Starkiller uses either some kind of hyperspace tunnel to funnel the star into itself, or possibly massive gravity generators / repulsors to form a tunnel that sucks in the star. Inside the Starkiller then would be rather than the star itself, some kind of system of containing it in hyperspace.

      In the movie they specifically called out that it used hyperspace to attack remote planets in other systems, and so the implication is that it’s funneling this energy through hyperspace to hit the planets.

      In other words, it sucks in a star to a hyperspatial storage system, then connects it via hyperspatial connections to the target planets. Some of this energy will be expended in setting up and maintaining all these hyperspace fields or whatever the terms are probably, but mostly you’re basically opening a portal from a star to a planet’s surface. BOOM!

        1. Yes If you can make wormholes you could just open up one between your target and something nasty, like a black hole. Or you could just open it ahead and behind the target then join the ends so that the target is pinched off into a pocket universe all on its own. That is the problem with being able to make black holes, they swallow up most possible plot lines too. :-)

        2. Well, in actuality, they’re just about both as insane as the other. Opening up a wormhole large enough to sustain the mass of a star travelling through it would requires orders of magnitude *more* energy than the star actually has in the first place. Think about it – you’re distorting spacetime far more than the star does already.

          So if you had that much energy in the first place, screw the star. :)

  6. “Doing the math for a weapons trench that is about 240km deep, a temperature of 0°C, and Earth-like atmospheric pressure and gravity on the Starkiller’s surface, we find the pressure at the bottom of the weapons trench is an astonishing: thousands of atmospheres of pressure. It’s a product of the exponential nature of the barometric formula, and save for force fields and gravity plating, there’s no way around it.”

    Exponential scale heights don’t work for trenches *that* deep. The reason that atmospheric pressure varies with height the way it does is that the mass you *lose* as you go down the atmosphere (the portion of it that’s *above* you) is negligible. That’s no longer true for a trench dug into a planet. Now you’re losing mass as you go deeper. Normally this would be negligible, however in the case of a trench *1/5th* the depth of the planet, that’s not true anymore.

    With constant density the scale height at the bottom of the trench would be 2x as high. The atmsophere just doesn’t weigh as much. With a bizarre density profile, you could find a way to reduce the static pressure in the trench. (That will cause other problems, though).

    Imagine if the entire planet is a completely hollow shell of ~1 km thickness, so the trench is just a support structure underneath that. The atmosphere in the trench would weigh *nothing* – the gravitational force exerted by a shell *inside* the shell is zero. So there’d be no pressure at the bottom of the trench all. Obviously that’s the limiting case of a “bizarre density profile”, which means you can generate any pressure you want (note that the pressure profile in the trench would still be super-weird).

    I mean, the planet already has to be made of unobtainium, since it has an average density of over 50 g/cc. That’s over 2 times the density of osmium, the densest naturally occurring element. So “bizarre density profile” isn’t that much crazier than the planet itself.

    But all that is just a static analysis. Because the atmosphere’s a fluid, any bizarre density profile like that would cause *massive* circulation effects as soon as you start spinning the planet.

    So, yeah. Not feasible. But then again, like I said, a planet with a density of over 50 g/cc isn’t feasible anyway.

  7. The movie never specified which Death Star, and the second one was anywhere from 160km to 900km in diameter. If we assume worse case and it’s 900km, than Star Killer base could be 9,000km which would make it about 30% bigger than Earth (about 6500Km)

    So unless someone can point out exactly which Death Star was specified, it can be anywhere from smaller than Earth’s moon to bigger than Earth.

      1. Still, the modulator or whatever it was was a big component on the surface (at 3/4 Earth size it would be the size of the USA), but it didn’t look so big in the attack scenes. Anyway, we probably need a smaller, deader planet (no continental crusts, cooled enough for that stupid trench to be dug out without making a lava torus, etc) for this.

  8. “But what exactly happens to this waste heat? Since The Force Awakens doesn’t show any radiators sticking up out of the atmosphere, so all of this energy must go into the atmosphere. ”

    Well, no. They dump the waste heat into hyperspace. Duh.

  9. Other potential problems to solve:

    1. Assuming you need just enough energy to destroy the planets as seen in the movie, how much of the star’s energy was actually needed?

    2. Wouldn’t it just be far far cheaper to make a giant space lens that focussed the light from the star onto the planet more effectively?

    3. How does the ‘star matter attracting tractor beam’ even work? Maybe the material losses from this process is where most of the star’s energy is lost – into space as unspent hydrogen/helium. I doubt efficiency of energy transfer is a concern with such a weapon if the answer to (1) is the expected tiny fraction.

    4. We see the starkiller planet turn into a tiny tiny star when it all goes wrong. How would you turn a K-type star into a 1200km diameter star? What would the gravitational effects be of sucking the star up over the course of several hours, and why didn’t the victims of the first attack notice this happening?

    5. Why did they have to dig a trench anyway?

    1. It seems you’re operating under the assumption that the weapon is in the same system as the target. Based on my understanding of dialog, the whole concept of the weapon is that it’s like the Death Star, but with the added benefit of not needing to be in the same system as it’s target allowing for far more stealthy attacks. Hence them referring to the weapon’s charge as traveling at hyperspace speeds; there would be no need for that if it were in the same system, but being in a different system it’d be absolutely required to eliminate the target in a sensible time frame.

      This would explain the need for a decent chunk of the energy used, as well as the surprise of the first attack.

      It may also be a possibility that not all of the star’s energy is being used for the weapon’s charge and acceleration thereof. If the planet needs to be mobile to get to the next star to consume I’d imagine it’d take a huge amount of energy to get the thing moving through hyperspace, so most likely they just hold on to a chunk of the energy for that.

      This still doesn’t explain the issues with the size of the star afterwords, but I could imagine that we’re only seeing the first stage of energy release as the systems tear themselves apart and fail. If they have to contain the energy of a star, I’d imagine they’re designed to withstand the forces of a star, so even when severely damaged it’d still take time for everything to be fully released.

  10. i think there is another possibilty to all of this. in the star wars universe they can travel way faster than the speed of light, even though they call it light speed. but they can cross huge distances in very short time. also they can communicate in realtime over great distances. from this i conclude that they have something like subspace or hyperspace. the laws of physics are different there. they mention in the movie, that the starkiller base can fire its weapon with hyperspace/subspace speed. which is way better than waiting x thousand years for the weapon to reach its target. assuming all of this, i think it is safe to assume that the weapon can store the stars energie also in subspace without all the nasty sideeffects. there is a strong evidence for this in the movie, when starkiller base gets destroyed, the star is “released” and reappears from within the base. that would not be possible if it had been converted to energie. up on the destruction of the base, the energie would have been released in a big explosion, but not as solar mass. maybe the base stored the sun in subspace and released it as a focused beam in subspace towards the target. it would not exactly be an energy weapon, more like something that throws solar mass at the target.

  11. Isn’t the atmosphere that high at the bottom of the Mariana Trench because of the water pressing upon it? I would think it’d be A LOT lower without the pressure of the water. The Trench puts a load of over 15k PSI, of what we call hydrostatic pressure. Mount Everest, is 29,029 feet and about 4.89 PSI, the Mariana Trench is 35,814 feet below sea level. The thin atmosphere at the altitude of Everest’s peak has only about a third of the pressure measured at sea level. So if we reverse that we’re looking at an atmosphere about a third heavier (more but I’m not doing the math), not 1000+ ATM.

  12. In the end, after starkiller base is destroyed, it appears to revert to a star. Perhaps that’s not surprising, since all the stellar energy is released, but a couple problems: 1) The *size* after reverting to a star is the same as the planet (instead of the presumed much larger original sun); 2) The new “starkiller sun” is certainly not in the same location as the original sun. The orbits of the original solar system will be totally hosed. Certainly enough time for evacuation, but I’ll call shenanigans if the same planet is the rebellion base. (Assuming the sun starkiller absorbed was the sun the rebellion base was orbiting around.)

    1. I was under the impression that the #1 benefit of Starkiller over the Death Star was that it didn’t have to be in the same system as the target. This would explain a lot of the “whoopty doo” behavior of, well, everyone really. If surprise were an important factor you’d want to pick a star in an uninhabited system, and if the system is uninhabited nobody cares if all the planets go flinging off into space as it’d take millennia for them to get anywhere (assuming they don’t get harvested first, I can imagine Star Wars galaxy inhabitants doing that to rogue planets).

  13. It would never work, you’d get located by gravity wave detectors the moment you started converting mass to energy at that rate. Then you would get taken out in a pre-emptive strike before you were ready to fire the thing.

      1. More idiotic selective logic from the green bum, if the detectors were spread across known space and they used hyperspace for communications you would know sooner. Duh! If you are going to subscribe to a bullshit fantasy universe you still have to apply the made up rules consistently.

  14. According to the calculator here http://www.mide.com/products/slamstick/air-pressure-altitude-calculator.php the pressure at 240Km below sea level is a staggering 2245216.14KPa (or over 22,000 times the air pressure at sea level on Earth), presuming that Starkiller Base has the same gravitational pull as Earth does.
    I’m going to make a wild suggestion: Maybe low gravity of such a small planet plus the depth of the trench means that the air pressure at the bottom of the trench is closer to that of sea level on Earth?
    Not forgeting that the Star Wars universe seems to obviously have artificial gravity generators (no-one is floating around inside their starship, all seem firmly anchored as if standing on an Earth-sized planet), which could be used to generate a suitable gravity on the base itself (and perhaps the immediate area) and stop the crew from accidentally launching themselves into orbit with every step or sudden movement.

      1. Yes. Which is why that calculator is wrong. It’s intended for finding air pressure in the atmosphere, not in a trench going down into the Earth. It’s assuming surface gravity is constant or close enough to constant.

        Surface gravity inside a uniform object is proportional to radius: so going down means surface gravity decreases, so each shell of atmosphere added weighs less and less.

        If the object isn’t uniform, it’s even more complicated, and the pressure could really be almost anything you want.

  15. Going waaaaaay out on a limb: what if the purpose of the all-important “thermal oscillator” was to distort space within Starkiller’s interior?
    Distorting space itself so precisely that the *distance* from the planet’s surface to the center of mass was equivalent to the radius necessary for a Dyson shell around the star?

  16. “Obviously it’s a giant death-ray that fires through hyperspace!” Exactly six years ago in Schlock Mercenary. http://www.schlockmercenary.com/2009-12-11 Go forward from there. Wanna cut Mr. Tayler a huge check for the concept, Disney?

    I saw the movie tonight. Also saw most of the bits and pieces of it already in the six previous movies. Abrams just dipped his hands into the candy dish of the past 37 years of Star Wars and picked out a few choice pieces to put together with a couple of new characters, Rey and Finn. Mix with current FX tech and what must be the most highly paid, non-speaking cameo appearance ever…

    We built this big battlestation, and they blew it up! We built an even bigger battlestation, and pretended it wasn’t finished, and they blew it up! We built an EVEN BIGGER battlestation that *eats stars and shoots through hyperspace*, and they blew up that one too! By the way, if we wanted to destroy the Republic, why didn’t we blow up Coruscant while we had the chance 37 years ago with the first Death Star?

    1. I felt the same. It’s a 2015 edition of the SW 77 on the fan side of things (while the prequels were Lucas side of SW).

      It is sad that Lucas is out because he would probably have been the bit of soil for “original idea” while Abrams and the rest would have taken care of keeping the 4-6 look and feel.

      So the prequels were too far off from 4-6, the sequel too close. I dream of a SWX that will .. bring balance to the universe.

    2. TFA is exactly what Star Wars needed. It was wise not to use too much originality on this first step, and what the writers came up with was clever and effective.

      “If we wanted to destroy the Republic, why didn’t we blow up Coruscant while we had the chance 37 years ago with the first Death Star?”

      Coruscant was the capital of the Empire at that point.

  17. One major thing glossed over in the movie… Once the STARKILLER uses up a Sun, then what?

    As we see in the final act, the base destroys a star and converts its energy inro some kind of plasma stream weapon. But once its used up a Sun, which it does in one or two shots, what does it do next? How does it get to the next star? Or is this the worlds most expensuve ‘one shot’ weapon? Does the STARKILLER base move an entire planet including its eco system using a hyperdrive? Thoughts?

  18. This all assumes that the entire mass of the star is consumed, and doesn’t take into account that the star would probably go supernova long before it explodes (propelling the planet outwards, and if it survives this it could use this to hop to another star [maybe the built it near a cluster of small stars]), this would mean that significantly less energy would go through the planet, although still probably a lot (would this be like a 1b type supernova because the outer hydrogen layer has been striped off, but it isn’t nearly as massive). Actually my main issue with the thing is that the energy required to destroy multiple planets is getting shoved through there atmosphere and yet it is still nice and snowy out, and that they seem to have Jakku temperature super conductors (I am assuming bb-8 has a few torque wheels inside that ball with a superconductor and some kind of magnetic tether around the outside of it), but hay there Kardashev 2.

  19. I have a funny feeling that a trench that deep will have some effect on the center of gravity of the planet, and that the mass of the weapon may be so high that the tidal effects are going to be impossible to deal with. So while they build the thing, before they could even start sucking up a star, they would already have a planet that’s trying to rip itself apart. You gotta respect the Empire engiineers for pulling that together. :-)

  20. Taking into account the number of 1/10 the diameter of the earth and the picture from above the trench is only 41 km deep (by fitting two circles with Inkscape). That would lead to an atmospheric pressure of 1.350e+07 Pa or 133 ATM with the barometric pressure formular and the assumption of 1 ATM at surface level. That is the same as diving 1.4 km deep.

    By assuming there is no weird stuff going on it is also possible to calculate the mass of the star destroyer with the diameter and m_SD = – (g r²) / G, with the assumption of same g at surface level and same gravitational constant. m_SD is then 5.980e+22 kg or 1 % of earth mass.

    With this information in mind it is also possible to calculate the gravity on trench level ( −1.121e+01 m/s² ) and therfore the afformentioned barometric pressure forumla is feasable.

    With 1.5 x 1031 Joules to absorb and the assumption that most of the star destroyer is out of water the delta T is 60000 K. So there is a problem :)

    See https://gist.github.com/Lageos/fcae8894dfd0050d46f7 for calculation (ipynb).

    1. “With this information in mind it is also possible to calculate the gravity on trench level ( −1.121e+01 m/s² ) and therfore the afformentioned barometric pressure forumla is feasable.”

      Surface gravity never *increases* going inside a uniform object. It *decreases*. Surface gravity inside a uniform object is proportional to radius, because there’s less mass. Assuming a uniform object with g=9.8 m/s^2 at surface, at 41 km down, gravity would be 93.2% of surface, or 9.13 m/s^2.

      Again, this is all assuming a uniform object, which planets usually are not. But since this planet is made out of unobtainium, who knows.

        1. Well, no – once you get rid of the uniform body requirement it could be literally anything. If you maintain spherical symmetry and assume that the trench itself is just a minor perturbation, 11.21 m/s^2 is the upper bound, which assumes that functionally all of the mass is inside the trench depth. Of course that increases the required density even past its already ludicrous 50 g/cc.

          There’s no lower bound, though. Put all of the mass in a thin shell at the surface, so the trench is just a pocket into a hollow body, and the surface gravity at the bottom would be very close to zero.

          Non-symmetric distributions could produce anything. It just depends what it is. Technically even the ‘Dyson sphere Starkiller’ would be bizarre, with the residual asymmetry acting to pull you to the walls of the trench.

  21. Very nice stuff here!. I’m no physicist (sadly), but glad to see someone has had the same thoughts on residual heat than me. As you say, Starkiller as well as both DS must have VERY good systems to dissipate the unavoidable waste heat, very far beyond puny thermal exhausts ports; otherwise they’d be vaporized when they fire.

    Saw the movie too, and while I agree they went overboard with it both in terms of design -the equatorial trench and the thing that absorbs and fires stellar plasma- as well as the fact it sucks up entire stars to fire, there’s a fact I notice all people here have overlooked: where are all those guns a base so big should have?. As far as I can remember, no anti-ship guns or any other type of defence besides a shield (don’t they have a backup shield or at least a backup control to raise it again?). Just TIE fighters and a escort of several warships.

    On the issue of its size, I think they were referring to the first Death Star (130 kilometers), as we see it totally built and not as the second one was when she was destroyed. That would make Starkiller of the size mentioned above.

    1. Sorry, I was wrong. There ARE defensive guns on Starkiller base, but it seems there’re not many of them -otherwise, with the experience of the destruction of both Death Stars the First Order could have converted the Resistance attack (just a bunch of one-man starfighters defeat a much larger vessel… sounds familiar) in a shooting gallery-.

      Likely it would have too anti-(capital) ship weaponry, that is not seen in screen.

      Still, it seems the First Order hired the same engineers who designed both DS for the Galactic Empire -same superweapon with a weak point that causes it to go BOOM with no safety measures-.

      1. Hey so I’m just confused by one thing. If you said 99.999 percent of it is used up and the rest goes to heat waste, how does that come out to 1.5×10^27 joules? Or is there some other calculation that you used to get that? I’m really curious but confused about it.

  22. Am i the only one who recognized that the term “sun” was used wrong? every System has a Star and the system is named after the star (correct me if im wrong with that). therefore our system = Solarsystem because our star is named the sun or Sol. so when this starkillerbase sucked up the sun it means its located in the milky way wich is wrong cause we know star wars takes place in a galaxy far far away…

    1. I’ve just have watched the movie and I think the same. It’s not logic to call “Sun” the star you are sucking the energy, because it means they are destroying our “Sun” , the star wich gives energy to our solar system, located un the Milky Way. So, if Star Wars is based on a far far away galaxy a long long time ago… It doesnt make any sense

  23. Didn’t they kind of explain it with that compresser/decoupler whatever thing – the big base thing that Chewy blew up. They said in the battle planning room that to store all of that energy they need “one of those things”. Deus ex machina.

  24. haven’t seen the movie, 4, 5, & 6 many times, 1,2, & 3 only once each and not all the way through, only read book 8 once and that was a long long long time ago in a state far far away, but with this star killer being so big, is disney compensating for something?

  25. this was funny to read, tho its possible that in that galaxy far far away DID exist genious engineers to adress all of the problems (afterall there was hyperspace, artificial gravity and lightsabers)
    what my problem is that some of the things broke the rules estabilished previously in sw films
    like: the energy/projectiles/whatever that actually destroyed the planets are showed to moved way too fast to travel through conventional ways, so the MAY travel through hyperspace BUT they’re clearly visible from other planets while vessels travelling in hyperspace are always invisible….

  26. I don’t know how you calculated 1.5*10^31 Joules, but you’re off by about 15 orders of magnitude.

    0.15 M_Sun * 2*10^30 kg/M_Sun = 3*10^29 kg

    E = mc^2 = 3*10^29 kg * (3*10^8 m/s)^2 = 2.7*10^46 J

  27. I was under the impression that StarKiller Base could not move from system to system and stayed in orbit around a single star. I also didn’t think that the StarKiller drained the ENTIRE star, but siphoned off a little bit at a time. Stars being big fusion reactions that last a long time, I figured that there was enough energy in one to be absorbed for many uses of the StarKiller.

    I took the line one of the characters said; “as long as there’s sunlight, there’s hope!” (or something like that) to mean that the weapon’s….sun material gathering took place while that particular piece of equipment (and the part of the planet the X-wing attack took place on) was pointed at the sun, and therefore the dimming of the light meant that the weapon was done accumulating energy and ready to fire.

    Maybe I have to rewatch the movie!?

  28. The Wookieepedia article about it states that, basically, the sucking of entire stars is just to power it up. Once it has enough energy, it’s stated it absorbs dark energy (a form of it named quintessence), transforms it to phantom energy and fires it to the target, causing massive disruptions in the space-time allowing the effects to be seen from thousands of light-years.

    While dark energy is real -and both quintessence and phantom energy are proposed forms of it, the latter intimately bound to the “Big Rip” scenario for the end of the Universe- the other stuff pretty much not. To starters, dark energy density is so low according to astronomers that Starkiller Base would have to suck up billions, if not more, of cubic kilometers of space (and since the SW events happened “a long time ago”, when dark energy was even lower than now, the problems increase). But, hey, this is Star Wars.

  29. Well physics in Star Wars universe may be different from our universe since, for example, sound seems to travel in space without a medium, unlike real life. Idk if any Expanded Universe work explained that or if it was in some guide, sorry, but if it wasn’t I assume physics are just different in the Star Wars reality.
    This was a very interesting post though!

  30. If the base emitted the mass of a star at the speed of light, wouldn’t the base be instantaneously accelerated in the opposite direction at such a rate that everone aboard would immediately die?

  31. What about the fact that the weapon from the base is energy. It travels at the speed of light. If the weapon targets multiple systems will would take years to impact the next star’s planet leaving enough time for an evacuation. Most useless mega-weapon ever!

    1. First, it is stupid. I’m not denying that.

      However, in the film it’s identified as a hyperspace weapon, that is, the beam travels at hyperspeed. How or why it’s still visible all along its path is anyone’s guess.

      There’s also the fact that since the EU purge, it hasn’t yet been reestablished that the speed of light is as slow in the SW universe as it is in ours. (And some scientists have proposed that “c” used to be much faster, which is good enough for sci-fantasy IMO.)

  32. Starkiller Base was what left me with the most questions as well. Honestly the rest of the movie was pretty well done, and freshly rebooted, but to make the overriding cataclysm a literal bigger version of a previous one seemed lazy. Also considering Abrams penchant for magical realism it seemed silly to have such giant holes poked into Starkiller Base so readily and easily: first that it drains it’s sun then (presumably?) moves on? Ok, well, we saw a bunch of trees on Starkiller Base, snow and clearly an atmosphere. Star Wars is geek history, from the dawn of the Internet. Since then, previously in depth scientific knowledge is now at everyone’s fingertips: it’s much harder to fool us and keep us satisfied. So Starkiller Base is basically “Earth” for the First Order and they’re just going to destroy their Sun to blast the Republic, destroying their own planet as well? I guess if anyone didn’t give a shit about their own planet it’s the First Order, and-ok, I’ve just now convinced myself that the First Order was readily prepared to destroy their own Sun and planet, for all intents and purposes, for a chance to quickly and completely destroy the Republic and Resistance. I’ve just convinced myself this wasn’t a plot hole at all.

  33. Aaaaand chicken out at the end as expected. If you have to critizese something than just do it. Without jumping out the escape door at the end. “It’s just a movie”…true. But a movie within the Star Wars universe that has established rules. That may or may not play a role in your argumentation but excusing every inconsistency now with this phrase leads nowhere.

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