Scientists are studying the strange behavior of a star located about 1,400 light years away, and they simply can’t figure out what to make of it. The discovery of KIC 8462852, Tabby’s Star, was made back in 2015, but two years later scientists still aren’t very close to figuring out why this star is suddenly dimming and then brightening again in a totally random pattern.

It’s led to some crazy theories, including the notion that perhaps it’s some alien megastructure like the Dyson sphere, a trope in science fiction. And now, it’s going through another dramatic dimming phase, causing scientists around the globe to train their telescopes on it to try to figure out what on Earth is going on.

It’s not uncommon for stars to dim, but that’s usually because of planets or clouds of dust passing in front of them, which happens on a regular schedule. This appears to be completely random, and the dimming is much more dramatic.

“A star known by the unassuming name of KIC 8462852 in the constellation Cygnus has been raising eyebrows both in and outside of the scientific community for the past year,” reads a 2016 statement from the Carnegie Institution for Science. “In 2015 a team of astronomers announced that the star underwent a series of very brief, non-periodic dimming events while it was being monitored by NASA’s Kepler space telescope, and no one could quite figure out what caused them. A new study from Carnegie’s Josh Simon and Caltech’s Ben Montet has deepened the mystery.

“Simon and Montet’s findings caused a stir in August, when they were posted on a preprint server while their paper was being reviewed. Now their work is now accepted for publication by The Astrophysical Journal.”