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takyon writes:

The dips in brightness observed at Tabby's star are still probably caused by dust, and not alien megastructures:

For the last two years, astronomers all over the world have been eagerly observing what is hailed as "the most mysterious star in the Universe," a stellar object that wildly fluctuates in brightness with no discernible pattern — and now they may finally have an answer for its weird behavior. Scientists are fairly certain that a bunch of dust surrounding the star is to blame. And that means that the more tantalizing explanation — alien involvement — is definitely not the cause.

It's the most solid solution yet that astronomers have come up with for this star's odd ways. Named KIC 8462852, the star doesn't act like any star we've ever seen before. Its light fluctuations are extreme, dimming by up to 20 percent at times. And its dips don't seem to repeat in a predictable way. That means something really big and irregular is passing in front of this star, leading scientists to suggest a number of possible objects that could be blocking the star's light — from a family of large comets to even "alien megastructures" orbiting the star.

Also at Sky & Telescope and Discover Magazine.

The First Post-Kepler Brightness Dips of KIC 8462852

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process.

Previously: Dust the Likely Cause of Tabby's Star Dimming

Original Submission