Could the Death Star Destroy a Planet?

In the movie Star Wars, the Darth Vader’s Death Star destroyed a planet. Could this really happen?

You’ve watched Star Wars right? Is that still a thing? With the Starring and the Warring? Anyway, there’s this classic scene where the “Death Star” sidles up to Alderaan, and it is all like “Hey Planetoid, you lookin’ fine tonight” and then it fires up the superlaser and destroys the entire orb in a single blast. “BOOM”. Shortly followed by some collective group screaming on the interstellar forceway radio.

This is generally described as “science fiction”. And when you’re making up stories, anything you like can happen in them. George Lucas’ hunger for your childhood toy money wasn’t hampered by the pesky constraints of physics in any meaningful way.

Here at the Guide to Space, we get to take our own flights of fancy and pointlessly speculate for your amusement. That’s our job. Well, that and snark. Let’s consider what it would actually take to destroy a planet with a ‘pew pew’ style laser beam, and what kinds of energy would need to be harnessed in a fully armed and operational battle station.

Let’s go back and carefully review our “evidence”. The Death Star drifts in, charges up all its lasers into a superlaser blast focused on Alderaan. The planet then detonates and chunks fly off in every direction just like the pie eating contest in “Stand By Me”.

What we saw was every part of Alderaan given enough of a kick so that it was traveling at escape velocity from every other part of the planet. If the Death Star hadn’t delivered enough explosive energy, the planet might have fluffed up for a moment, but then the collective gravity would suck it all back in together, and then the slightly re-arranged, and likely now uninhabited planet would continue orbiting its star.

You can imagine doing this the slow way. Take each continent on Alderaan, load it up into a rocket and blast that rocket off into space as though it was on escape trajectory from the planet. Sure, you’d would need an incomprehensible number of rocket launches to get that material off the planet. But hey, midichlorians, blue finger lightning and ESP.

Fortunately, as you carted away more and more of the busted up rock, it would have less mutual gravity, and so the rocket launches would require less and less energy to get the job done. Eventually, you’d just be left with one last chunk of rock that you could just force ninja kick into the neighboring star.

Death Star beam. Credit: Lucasfilm
Death Star beam. Credit: Lucasfilm

So how much energy is that going to take? Well, there’s an “easy” calculation you can make. The energy you’d need is equal to 3 times the gravitational constant (6.673 x 10^-11) times the mass of the planet squared divided by 5 times the planet’s radius. Do this math for an Earth-sized/mass world, and let’s see that’s, two and one, carry the 5… and you get 2 x 10^36 joules. That’s a two followed by 36 zeros in joules. Is that a lot? That sounds like a lot.

Well, our own Sun puts out 3 x 10^26 joules per second. So, if you poured all the energy from the Sun into the task of tearing apart the Earth, it wouldn’t have enough energy to do it. In fact, you’d need to focus the light of the Sun for a full week to get that level of planet destruction done.

According to ancient Star Warsian dork scholars, the Death Star (SOLUS MORTIS) is powered by a hyperreactor with the output of multiple main sequence stars. So there you go, problem solved. It’s the size of a small moon, but it’s more powerful than many stars. Of course it can destroy a planet.

Exploding planet. Credit: ESO
Exploding planet. Credit: ESO

The Death Star clearly destroyed Alderaan. We watched it explode. I saw it, you saw it. We heard the screams of millions of souls cry out. It happened. But what if it wasn’t a beam thingy?

Our math is good, but clearly we’re not enlightened enough to comprehend the true wisdom hidden within the Lucasian scriptures. Perhaps the Death Star’s superlaser was just a targeting laser. Directing the placement of gigantic antimatter bomb. According to Ethan Siegel, from “Starts With a Bang,” you’d only need 1.24 trillion tonnes of antimatter.

Imagine you made a bomb out of that much antimatter iron – if that’s even a thing – you’d only need a sphere about 3 km across. If the Death Star is 150 km across or so, they could carry a bunch of these. Very carefully. Like super carefully. Okay, maybe it’d be a good idea if everyone took off their boots, and make sure they only talked with their inside voices.

Obviously, Star Wars is a story, so anything, ANYTHING can happen. The future is unknown, and we might discover all kinds of weirdo physics and harness them into all kinds of powerful weapons. I’m only suggesting, that a space station capable of deploying a week’s worth of solar energy in a single second might be a stretch. And maybe, George, if you just done a little back of the napkin math, we wouldn’t be talking about this right now. Also, maybe no Ewoks. I’m just saying.

Where do you stand on the feasibility of imaginary space station weaponry? How big a planet can your imagination destroy?

12 Replies to “Could the Death Star Destroy a Planet?”

  1. Perhaps hoping for less snark and more fun…. consider that the beams of the laser meet and change direction – and that this happens over a Dish in the surface of the Death Star.

    Light isn’t going to change direction based on encountering other light. So suppose it is a system for generating a dark matter (HA! you can’t see it) particle particularly good at converting iron nuclei into antimatter particles and that interaction changes the direction of the lasers (note they are also carrying pulses like particles excited with the light) so you get enough matter conversion so the planet blows itself up and can still be focused by the Dish of the Death Star. Probably would take a lot less power to actually make happen – more in the arena of a catalyst.

  2. If you can suspend disbelief to allow faster-than-light travel, blowing up a planet in a couple of seconds is no stretch at all.

    1. If they have FTL travel and needed to blow up a planet, they’d do better to just accelerate a projectile to superluminal speeds and let it hit the planet. It would be carrying a tremendous amount of kinetic energy, and there is no way the victims could see it coming.

  3. Would have been easier to just accelerate a Star Destroyer (like a old model that no Imperial Starship Captain would want to be seen in) to the speed of light and fly it into a planet. Star Destroyer’s are something like 5 to 10 miles long and the Empire has plenty of them. A five mile diameter asteroid flying at 0.01% the speed of light causes mass extinction on Earth. A C-speed flying Star Destroyer probably wouldn’t discombobulate the “mass” of “an entire planet”, but the goal of the Evil Empire is probably just to kill everything off on the planet. That way they could make the planet into a base. If you totally make the planet go “BOOM” and turn it into a new asteroid belt, it won’t be of much use (except to maybe Han Solo).

    1. You know, I really hated the Ewoks. But then, after Jar-Jar came along, I began think maybe the Ewoks weren’t really so bad.

  4. This is the type of stuff we would talk about in college after smoking a joint…..Fraser???

  5. Fraser! What took this topic so long?!?!? And the Death Star belonged Grand Moff Tarkin, not Darth Vader. Booo to your use of the Praxis inspired Alderaan explosion. Good vid.

  6. Look, Frasier, you’re a brilliant guy and you run a great site, but the power to destroy a planet is INSIGNIFICANT next to the power of the Force.

  7. Ok, sorry but I have to disagree. The disclaimer was probably the most accurate part of the video. Here is what I mean: We know that these people have Subaru-sized runabouts (x-wings) that can reach warp. So, is it that improbable to have something “the size of a small moon” have that type of power? Next, the actual “how” should be considered a little more closely. For example, if we are to believe Einstein’s E=mc^2, then energy and matter are simply 2 sides of the same coin. So, instead of an “explosion” as we know it, simply catalyze a reaction that turns a planet’s core from matter to energy and snowballs (since we are taking creative liberties here). As far as the lasers “joining”, there might be an explanation there too. If you look closely, the “beams” unite, but there is an additional “orifice” behind the “joining” point. What comes out of there? Maybe it’s a “concentrated anti-matter” that the lasers are “reconstituting”. Makes keeping antimatter more feasible and safer. I am guessing. And to finish up, let’s carry this idea to the Vogon constructor fleet. That one seems a bit tricky.

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