For the last few years, a distant star in the constellation Cygnus, known officially as KIC 8462852 and unofficially as Tabby's star or the WTF star, has intrigued astronomers due to its irregular but significant dimming. Astronomers have struggled to find a natural explanation for why the star dims so much, 20 percent, before returning to its regular brightness.

These observations have led to various hypotheses, including the exotic notion of some kind of alien megastructure passing between the star and Earth-based telescopes. Now the enigmatic star has been observed to be dropping in flux again, and astronomers have put out a call for telescopes around the world to measure light coming from the system.

As of Friday morning, it appeared that the light curve coming from the star had only just begun to dip, offering observatories a chance to observe most of dimming cycle.

A few recent scientific papers have offered new theories about what may be producing the dip. One new idea is that an internal process within the star may be causing its global magnetic field to flip, leading to a change in flux. Another research paper suggests that, rather than comets passing in front of the star as earlier hypothesized, the lower fluxes are caused by dust clouds associated with massive parent bodies orbiting the host star.

The only way to unravel this stellar mystery is through more observations from Earth-based telescopes, because it's not like we can send a probe to Tabby's star any time soon—it's nearly 1,300 light years away. So the next best option is to observe it as much as possible when its light curve is dipping. Which means right now.