What’s causing Tabby’s Star to act so weird?

A cool disc may be blocking out its light

We’ve observed stars that dim in brightness for a few days like this star, but they are all very young and have giant discs of gas and dust around them. In those cases, we know the disc is coming between us and the star, blocking the light. As far as we can tell, Tabby’s Star (KIC 8462852) isn’t young and it doesn’t have a big disc around it. It’s possible that there’s a small, cool disc in a wide orbit far away from the star, or that there’s a cloud of gas in the interstellar medium, the space between stars, that's passing along our line of sight and blocking the light. For both of these scenarios, we have predictions for what the light would look like at different wavelengths during another big dip. Now we are waiting patiently for another dip, and will record data as soon as we see one to test both of these hypotheses.

Dr Ben Montet,