Diehard Star Wars fans have speculated for a long time about the origins of Starkiller Base, the planet-killing super-weapon featured in Star Wars: The Force Awakens, and now a popular theory has been officially confirmed. According to fan theories, the snowy planet into which Starkiller Base was built was, in fact, a long-established Star Wars planet called Ilum, the source of the blue and green crystals that power Jedi lightsabers. Ilum was first introduced all the way back in 2001, as the setting of a junior novelization following the adventures of a young Anakin Skywalker, but its inclusion in the animated series Star Wars: The Clone Wars allowed it to be grandfathered into the current Star Wars canon in 2014. In all appearances, Ilum has been a lifeless, icy world notable only for its caverns filled with naturally-occurring Kyber crystals. The Jedi controlled the planet for thousands of years, sending apprentices to Ilum as part of their trials to become full Jedi Knights.
Fans noted the basic similarities between Starkiller Base and Ilum in 2015, when The Force Awakens first came out, but the theory really picked up when Rogue One: A Star Wars Story revealed that Kyber crystals were also used to power huge super-weapons like the Death Star - making the planet an ideal choice for the First Order's Starkiller Base. There's also an official Star Wars galaxy map which placed Starkiller Base's origin point in the same part of space as Ilum, and a canon novel which revealed that the Empire strip-mined the icy world immediately after it rose to power in Star Wars: Revenge of the Sith. With all of this evidence in hand, fans had a compelling argument in favor of Ilum and Starkiller Base being one and the same.
But, just in case "basically confirmed" wasn't enough, Reddit users on r/StarWarsLeaks did some mining of their own - in this case, data-mining through the unreleased files of the upcoming game Star Wars: Jedi: Fallen Order. According to images retrieved by the Reddit users, Ilum is a location that will appear in the game - and the Empire's mining efforts have, by this point in time, made it look almost exactly like Starkiller Base eventually will 30 years in the future.
It probably shouldn't be surprising to learn that Ilum and Starkiller Base are the same planet. If there's one thing the Lucasfilm Story Group, the people responsible for getting Star Wars canon straight, love to do, it's make connections between stories from different eras (and mediums) of the franchise. That is, after all, why Darth Maul returned to live-action at the end of Solo: A Star Wars Story, cluing many fans into his survival for the first time, and why the newly released show The Mandalorian features references to the prequels, the animated series Star Wars: Rebels, and more in just the first episode.
Still, confirmation that a sacred Jedi planet was turned into a horrific weapon of mass destruction has a note of tragedy to it, especially given that players in Fallen Order will take control of a Jedi survivor struggling to come to terms with the deaths of his former comrades. Jedi: Fallen Order will be released on November 15, 2019, so Star Wars fans won't have to wait long to learn more about this legendary planet.