[LINK] On the latest surprises from KIC 8462852

[rfmcdonald]

Distant star KIC 8462852/a>, known for its very unusual dimmings, continues to produce surprises. The Dragon's Gaze recently noted one paper suggesting that the level of interplanetary dust around this bright star is low enough to exclude the possibility of something catastrophic like a planetary breakup, providing evidence in support of the thesis that the dimmings were caused by the incursion of a family of comets. But then, we also recently got this, Bradley E. Schaefer's paper "KIC 8462852 Faded at an Average Rate of 0.165+-0.013 Magnitudes Per Century From 1890 To 1989". Drawing on his naked-eye analysis of archived images including some more than a century old, Schaefer identifies a much older pattern.

The star KIC 8462852 is a completely-ordinary F3 main sequence star, except that the light curve from the Kepler spacecraft shows episodes of unique and inexplicable day-long dips with up to 20% dimming. Here, I provide a light curve of 1232 Johnson B-band magnitudes from 1890 to 1989 taken from archival photographic plates at Harvard. KIC 8462852 displays a highly significant and highly confident secular dimming at an average rate of 0.165+-0.013 magnitudes per century. From the early 1890s to the late 1980s, KIC 8462852 has faded by 0.193+-0.030 mag. This century-long dimming is completely unprecedented for any F-type main sequence star. So the Harvard light curve provides the first confirmation (past the several dips seen in the Kepler light curve alone) that KIC 8462852 has anything unusual going on. The century-long dimming and the day-long dips are both just extreme ends of a spectrum of timescales for unique dimming events, so by Ockham's Razor, all this is produced by one physical mechanism. This one mechanism does not appear as any isolated catastrophic event in the last century, but rather must be some ongoing process with continuous effects. Within the context of dust-occultation models, the century-long dimming trend requires 10^4 to 10^7 times as much dust as for the one deepest Kepler dip. Within the context of the comet-family idea, the century-long dimming trend requires an estimated 648,000 giant comets (each with 200 km diameter) all orchestrated to pass in front of the star within the last century.

Centauri Dreams looks at this, with an extended discussion in the comments. Speaking as a non-astronomer, all I can say is that this points to Kepler's discovery of something very interesting. If this dimming trend has been ongoing for some time, KIC 8462852 is unusual. Whether this has something to do with KIC 8462852 itself--perhaps a very rare long-term variable, or even a perfectly normal star caught at a stage of its life not yet suspected?--or whether it involves peculiarities of the system, even extraterrestrial megaconstructions, is uncertain.

I hope we can find out.