Science fiction writer L. Ron Hubbard's most notorious space opera is the religion of Scientology, which is packed with aliens and space battles and waves of invaders to our solar system. Hubbard even referred to the cosmological timeline behind Scientology as "the space opera," and for good reason. It reads like a pretty damn trippy science fiction novel. For your edification, we've created a handy timeline (below) that compares the scientific history of the universe with the Scientology history of the universe. Who knew all that alien stuff was going on during the middle ages? And before the Big Bang?
A few notes for the uninitiated. According to Scientology, "Thetans" are aliens whose spirits live within humans today. So Thetans are kind of like proto-humans. Also, within the Scientology time frame, the biggest incidents usually involve the Thetans being traumatized with "implants" or "brainwashing" from other aliens. So you'll see a lot of references to various brainwashing incidents here, including the invention of the Christianity Implant, which Hubbard believed was a very corrosive form of mind-control. Illustration by Stephanie Fox.
Sources on Scientology cosmology: Wikipedia, Operation Clambake.