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## January 11, 2012

### Could the Death Star Destroy a Planet?

The first Death Star from Star Wars (via Wookieepedia)

Obi-Wan: That’s no moon. It’s a space station.

That space station was the Empire’s first Death Star in Star Wars: A New Hope. Obi-Wan and company had just bounced through a debris field, the remnants of the planet Alderaan. Such an act of destruction would seem impossible to us–it seemed so to many of the movie’s characters until it happened. But perhaps not, say three students at the University of Leicester in England who last year published a study on the subject in their university’s undergraduate physics and astronomy journal.

The study’s authors start off by making some simple assumptions: The planet being fired upon doesn’t have some sort of protection, like a shield generator. And it’s about the size of Earth but solid through and through (Earth isn’t solid, but the planet’s layers would have significantly complicated the math here). They then calculate the planet’s gravitational binding energy, which is the amount of energy required to pull apart an object. Using the mass and radius of the planet, they calculate that destruction of the object would require 2.25 x 1032 joules. (One joule is equal to the amount of energy required to lift an apple one meter. 1032 joules is a lot of apples.)

The energy output of the Death Star isn’t given directly in the movie, but the space station was said to have had a “hypermatter” reactor that had the energy output of several main-sequence stars. For an example of a main-sequence star, the authors look to the Sun, which puts out 3 x 1026 joules per second, and they conclude that the Death Star could “easily afford to output [the energy required for an Earth-like planet's destruction] due to to its tremendous power source.”

It would be a different story, though, if the planet scheduled for destruction had been more like Jupiter than Earth. The gravitational binding energy of Jupiter is 1,000 times that of the Earth-like planet in the study. “To destroy a planet like Jupiter [the space station] would probably have to divert all remaining power from all essential systems and life support, which is not necessarily possible.”

Of course, that assumes that the Emperor wouldn’t be willing to sacrifice a space station full of people to wipe out his enemies. And considering that he was just fine with wiping out whole planets, I’m not sure I’d take that bet.

***

1. Mike Simpson says:

Thanks for writing about Physics Special Topics. This unique in-house journal gives undergraduate Physics students at the University of Leicester the chance to participate in a peer-review process on each other’s work, thereby preparing them for publication in better-known journals. Though topics may be flippant, all the physics must be rigorous and accurate; the students will reject each other’s work if not up to scratch. Other topics in the current issue include the requirements of Bruce Willis’ asteroid-smashing nuclear weapon; the physics of a falling Batman; the likelihood of a Gamma Ray Burst destroying life on Earth; and how much younger six-times Formula 1 world champion Michael Schumacher is than a hypethetical identical twin due to the relativistic effects of his high-speed career!

2. Nick Ring says:

Thanks for the comment, Mike – it sounds like a wonderful program!

3. imma says:

3×10^26 (=3e26) joules per second per star
several ~7* => 2.1e27 joules per second per deathstar
*nice number chosen for convenience, but it seems reasonable

needs 2.25e32 joules – ~ 1e5 seconds = 100000 secs
= 27.8 hours to destroy earth

4. imma says:

so jupiter would take ~3 years, methinks

5. Richard says:

great entry, but wouldn’t it be more useful to give an actual link to the article and or the publishers names so we can read it for ourselves.

6. Sarah Zielinski says:

Sorry about that. Here it is: https://physics.le.ac.uk/journals/index.php/pst/article/view/328

7. Fletcher says:

Well, I think that’s obviously why the Emperor ordered the construction of the 2nd Death Star – bigger, better, etc.

“Little does Luke know that the GALACTIC EMPIRE has secretly begun construction on a new armored space station even more powerful than the first dreaded Death Star.” – Courtesy of Wikiquote

8. Merennulli says:

This fits with the movie, since they had to fly the Death Star around the planet Yavin to reach it’s moon Yavin IV when they planned to destroy it due to the Rebel base there.

It’s an often-criticized part of the movie with claims that a planet-destroying weapon wouldn’t wait to move around a planet to destroy another planet. This strongly implies that it made sense, though I doubt it was actually thought out beyond it’s dramatic impact by the writers.

9. Ben says:

This is not the webpage you are looking for…

10. Jared says:

It seems to me that these assumptions that it would take years to destroy a large Jupiter-like planet are assuming that you are just shooting the core of the planet. It would save much more time to blast off the edges of the planet in the case of a large one.

11. Dash says:

I loved reading all these comments! It’s good to know that we geeks are quite a powerful force in the world today :)

12. Alex Simring says:

It’s great seeing a blend between science fiction and science! I think it helps to keep students motivated and interested. When education becomes ‘relevant’ it’s more exciting. What starts of as fantasy may yet in the future become reality… look at the invisible cloak, and who knows, maybe even time travel in the not too distant future.

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