KIC 8462852, a star with a name a bookkeeper would come up with, has scientists baffled. Data sent back from the Kepler Space Telescope, specifically launched in 2009 to search for Earth-like planets orbiting other stars, was confusing. The star, nicknamed the WTF-star (“Where’s The Flux”…), exhibited strange light fluctuations, up to the point that even SETI got involved and started looking for radio emissions. They found none thus far by the way.
Several hypothesis have been brought to the table, from comet swarms, interstellar dust to asteroid fields. None were fully satisfactory. Apparently the scientific community had to work up the courage to finally propose a fringe possibility, alien activity. Perhaps a Dyson sphere, a device that encapsulates a star, and harvests most of its energy. Of course this would indicate an alien race so advanced that our best hope is that they never contact us.
When I was reading up on Dyson, I learned he also did some thought experiments on self replicating systems, something I first read about when The Game of Life (Conway) was featured in a school project. While as a concept, the 2-state 2-dimensional cellular automaton was simple enough, as a programming assignment it proved challenging (but fun). The idea of non-biological self replicating machines was first explored by Von Neumann, and the name Von Neumann machines is sometimes used as a general label. So if not a Dyson sphere messing with KICs light, then maybe a Von Neumann machine, activated millennia ago. And to spice things up, these machines can go rogue too (well, at least in science fiction).