KIC 8462852: How a Mysterious Star Went from Alien Megastructure to Dust Magnet

alien megastructure star
An artist's impression of KIC 8462852, a mysterious star more than 1,400 light-years away. NASA/JPL-Caltech

New observations of perhaps the weirdest star scientists know have finally put to rest one of the most engaging hypotheses to explain its wild behavior: that aliens had built a giant structure around it that was occasionally blocking some of its light. But what is the star, and how did such an odd idea gain traction?

The star is nicknamed Tabby's Star after Tabetha Boyajian, an astronomer at Louisiana State University who has led its study, and formally known as KIC 8462852 because the first truly detailed observations of it came from NASA's Kepler Space Telescope. That instrument is designed to hunt exoplanets by looking for the small dips in brightness that occur when a planet passes between its star and the telescope. During the telescope's heyday, between 2009 and 2013, it stared at 150,000 stars, trying to spot these tiny changes, in the process identifying 2,341 exoplanets.

As part of that work, it also monitored KIC 8462852. But unlike the small, orderly brightness dips caused by exoplanets, the KIC 8462852 data was much stranger. Dips lasted anywhere from five to 80 days (exoplanet dips usually last a few hours) and robbed the star of as much as a fifth of its brightness (compared to 1 percent by a large exoplanet).

Weirdly, at first the dips hadn't caught the attention of computers poring through Kepler's data—they went unnoticed until a team of citizen scientists decided to see if there was anything the automated searching might be missing (the same team has identified missing planets that way as well). The early observations were published in a paper titled simply, "Where's the Flux?" after an astronomical term referring to a star's brightness as affected by distance, and to reflect the scientists' discomfort with a paper so full of guesses, albeit educated ones.

The star wasn't young enough to be surrounded by dust still forming planets. Maybe there were hundreds or thousands of giant comets circling the star. Maybe a Death Star-like planet destroyer had created new dust blocking the star. Another astronomer who had been wondering whether Kepler could identify a giant alien-created structure thought the dips looked awfully suspicious, like a way of capturing the star's energy for a civilization that has run out of fuel.

The SETI Institute, which is named for its work searching for extraterrestrial intelligence, although its scientists tackle a much broader range of scientific puzzles, studied the star as well. That work used the institute's powerful Allen Telescope Array of radio telescopes designed to eavesdrop on radio signals produced by technologically advanced alien civilizations. They didn't find anything.

Read more: Alien Megastructure Is Just A Really Weird Star Surrounded by Dust, Says New Analysis

In February 2016, Boyajian presented a TED talk about the star and its antics, which has been viewed more than three million times. And in July 2016, a Kickstarter project raised just over $100,000 in two months to fund continuing observations of the star. Those observations took place over much of 2017 and created the data that was used in the new paper, which focuses in particular on a dip that was observed in May 2017. Scientists are currently focused on analyzing three more subsequent dips. But the new paper confirms that the dips were made by something fairly transparent and with small particle sizes, like dust, rather than something large and opaque like a structure.

Right now, the star is out of view, but it's due to become visible again in late February or early March, when Boyajian's project will resume studying it. That project is currently funded through the summer, although she says she would feel more comfortable given the star's unpredictable nature if monitoring resources were confirmed for the next decade.