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Weird dim star isn't due to alien megastructure - it's just dust

12 January 2018

The papers, authored by more 200 scientists from across the globe and published on the pre-print site arXiv, present new light measurements that indicate the fluctuations from the star, KIC 8462852, that had baffled scientists for several years are instead caused by very small particles of space dust. But some unusual behaviour was observed in October 2015.

That's the view of a new paper by Louisiana State University astronomer Tabetha Boyajian and scores of co-authors - including astronomers Brett Morris and James Davenport from the University of Washington.

The answer that seems the most likely is that a massive cloud of dust is circling the star, blocking out light at intervals.

"Ground-based follow-up observations to better characterize the star revealed nothing other than KIC 8462852 being an ordinary, main-sequence F3 star: no peculiar spectral lines, Doppler shifts indicative of orbiting companions, or signs of youth such as an infrared excess".

Boyajian noted that if something like a planet were blocking the light, it would block all wavelengths by the same amount.

"It's been called the most mysterious star in the galaxy, we call it the "WTF" star." said Jason Wright, one of the astronomers who studied Tabby's Star, in an interview by the Business Insider. "And this is exactly what we see", Boyajian told CBC News in a recent interview.

Boyajian said, "It's exciting".

"That's the first time we ever saw the star get bright and faint again".

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After studying the four dips - named Elsie, Celeste, Scara Brae, and Angkor by crowdfunding supporters - the researchers found that the dimming was much more pronounced at some wavelengths, and less intense at others.

KIC 8462852 is nicknamed "Tabby's Star" after Boyajian, who discovered it with the help of citizen scientists.

But new observations suggest the real culprit is dust - perhaps the remains of a planet or moon the star recently destroyed.

A chart showing one of the dips in KIC 8462852's light, with different wavelengths. This variable dimming where more blue light is blocked than red light is what scientists would expect if something more diffuse was responsible, like clouds of dust or shattered comets, Wright explained in a blog post about the data. This, she concludes, means that whatever is causing the odd dips isn't opaque as one would expect with a Dyson Ring. "Larger dust that is created survived and remains on a circumstellar orbit spreading from its point of origin in a manner similar to comet dust tails, causing the secular dimming". "There's still the possibility that whatever's going on is something we haven't thought of and that it's not dust at all", Boyajian says.

"It drives me a little insane", Boyajian said. The theory excited academics in SETI science (Scientific Searches for Intelligent Extraterrestrial Life), the general public and headline writers alike.

"I think that's the coolest part of this star, as frustrating as it is, is that it kind of puts us all in our place, saying, 'Okay we don't know everything'". And Boyajian ran a heck of a good Kickstarter Campaign, giving people a chance to participate in science, and keeping those who donated informed every step of the way via frequent updates.

Between March and December 2017, the researchers observed four distinct episodes where the star's light dipped by up to 2.5 per cent.

It makes them more interesting to professional astronomers, probably.

Weird dim star isn't due to alien megastructure - it's just dust