Physics of Star Killer Base

If you haven't seen the latest Star Wars ("The Force Awakens", episode 7), stop reading immediately! :)


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Apparently, there has been some griping about the physics of Star Killer Base.

For example, if the planet can't move, and even one shot substantially drains their sun - then you've only got a few shots from your super-weapon (not to mention everyone on the planet will freeze).

Also, if the weapon drains the whole star, then it is really massive overkill (about 12 trillion times according to one site).


There is a much more reasonable explanation!


The photosphere is the region of the Sun which emits visible light.  The key idea is "It [the photosphere] extends into a star's surface until the plasma becomes opaque"

If you strip off the photosphere, then the star will appear opaque i.e. black (at least, until it regenerates).

Ok, so how much energy can you get from the photosphere (we'll assume the Empire, err, First Order, has sufficient tractor beam and shield technology to extract it quickly and safely).


All of my calculations are in a Google Drive spreadsheet.


Final result?  Yes - there's about 1700 times more power than you need to blow up one planet just from fusing the hydrogen in the photosphere into helium (you could get more power by fusing up to iron).


And how rapidly could you fire such a weapon?

I'm not sure of the fluid dynamics, but keep in mind the regions of the photosphere last about 8 minutes (they are upwellings of cooling plasma).  Which implies it might recharge very rapidly indeed!