In science fiction, a planet killer is an entity, often a large spaceship, expressly designed to destroy or render uninhabitable a planet. The most famous planet killer is the Death Star, though many others have seen film or print. Most major science-fiction franchises, including Star Wars, the Starflight series of computer games, Wing Commander, Babylon 5, Star Trek, Lexx, Farscape and Stargate SG-1 have at least one such device.
The Star Wars Expanded Universe uses the term "superweapon" for such a device.
To kill a planet
Science-fiction writers have devised many methods of destroying a planet: you can blast it with a laser, you can launch nuclear missiles at it until the air hums with radioactivity and the surface glows red, or you can use exotic energy weapons not covered by present-day physics. The defining criterion is that the weapon must at least destroy the planet's entire ecosystem and make it forever uninhabitable afterwards; a more thorough tactic is to physically demolish the planet itself. Genre writers, being ever-creative to one-up each other's worst atrocity machines, have created many designs to fulfill both of these purposes.
In order to completely disperse a planet, one must supply at the very least enough energy to overcome its gravitational binding energy. One can supply more than this, of course, to overcome inefficiencies or to make the planet's dispersion more spectacular. The king of brute-force planet destruction is the Death Star, whose energy output has been estimated to equal the Sun's output for over thirty thousand years in a single blast.
Most writers, working in a print medium and unable to match the visceral chill of a short film sequence of an obviously life-bearing blue marble world being turned into a brilliant fireball in less than a second, prefer to use slower methods of planet destruction, making up in pathos what they lack in instantaneous impact. Under such a constraint, planet destructions are often much slower affairs, taking minutes, hours, sometimes even days for the protagonists to act or simply reflect upon their fate. The classic exception to this rule is probably Douglas Adams's The Hitchhiker's Guide to the Galaxy, the print version of which destroys the Earth in three sentences:
- There was a terrible ghastly silence.
- There was a terrible ghastly noise.
- There was a terrible ghastly silence.
When categorizing such apocalyptic instruments, one should note that several devices—Asimov's Electron Pump or the 27th century Tox Uthat, to name a couple—operate not by destroying a planet, but by annihilating the star which it orbits. The absolute energies involved here can exceed that produced by the Death Star's blast, but they are generated indirectly. Finally, inventions like Egan's Ensemble mod are too esoteric to admit classification by energy output.
Famous planet killers
Babylon 5
Lexx
Star Wars
Star Trek
Various computer games
Various films, television and radio programmes
Various novels and written sources
