For years, one star made astronomers question everything they thought they knew about how starlight dims. It’s called KIC 8462852, though the world knows it as Tabby’s Star. It sits 1,500 light-years away in the constellation Cygnus, and in 2015 the Kepler telescope recorded something that shouldn’t be possible: its brightness dropped by as much as 22%, suddenly, without warning, and never repeating the same pattern twice. To put that in perspective: if Jupiter passed in front of our Sun as seen from far away, it would block barely 1% of its light. Something was blocking almost a quarter of that star. One hypothesis became legend: a Dyson sphere, a…