Disney/Lucasfilm
The most horrific weapon used in "Star Wars: The Force Awakens" is the "Starkiller Base," a massive laser used to blow five planets in the Hosnian System - including Hosnian Prime, home to the New Republic's capital - to bits. But how the deadly weapon works was barely explained at all in the film.
Finn (John Boyega) briefly explains that the weapon was supposed to drain the energy from stars and then store the energy in the planet's core, where it was eventually shot through a canon to destroy whatever was in its path.
While the "science" behind that sort of weapon doesn't exactly exist, the film's novel, written by Alan Dean Foster and signed off on by Disney/Lucas Films, goes more in depth, explaining how the base was formed and what it's purpose was.
Starkiller Base was an altered planet, the book explains, which allowed it to be both a weapon and base.
"Spectacular and isolated, with a mean surface temperature varying from merely cold to permanently arctic, the planet had been altered: its mountains tunneled into, its glaciers hacked, and its valleys modified until it no longer resembled its original naturally eroded form," Foster wrote.
Rather than suck power directly from stars, the weapon used the power from stars to collect dark energy, "known as quintessence," which was held in a containment unit in Starkiller Base's core until the weapon was ready to use and then shot through a hollow cylinder.
"At incredible velocity and accelerating exponentially, the concentrated volume of quintessence escaped, transforming as it did so into a state known as phantom energy and following the artificial line of egress that had been provided. Assuming that the rotation and inclination of the planet had been taken into account, the released blast of concentrated phantom energy would travel along a perfectly linear path, punching a small Big Rip through hyperspace itself until it left the galaxy."
Later, Finn described this "Big Rip" as "'sub-hyperspace" when explaining the weapon to the Resistance.
After striking the planet of Hosnian Prime, the energy went through the crust and mantle and ignited the planet's core, "turning the planet into what astrophysicists called a pocket nova."
The explosion caused a burst of heat that expanded to the other planets in the Hosnian System and obliterated any sign of life.
Admiral Statura (played by Ken Leung in the film), determined that Starkiller Base's weakness was its oscillator.
"A planetary magnetic field, even a strong one, would not be enough to contain the amount of energy that we have seen deployed," he said. "Also as you say, Finn, there is more involved. I am thinking some kind of oscillating field. If it oscillates rapidly enough, much less energy would be required to sustain it than if it was maintained at a steady state."
The Resistance's attack and eventual destruction of the oscillator caused the Starkiller Base to ultimately implode.