Chaotic dimmings puzzle astronomers

Data from Kepler revealed several mysterious dimmings.

The Kepler space telescope has kept an eye on KIC 8462852 for four years, during which the star's brightness has fallen twice, by 16 and 21 %, plus several minor dimmings. This type of star should be stable. Something unknown must block out the light of the star at irregular intervals. It cannot be other planets, as they would reduce the starlight no more than a few % at regular intervals.