Space is filled with unsolved mysteries, but rarely do they rivet astronomers and sci-fi fans the way KIC 8462852 has. In 2015, researchers announced that the distant star's light had periodically waned over the course of several years (once by as much as 22 percent), prompting some to theorize that a type of power-harnessing "alien megastructure" could be the culprit. This explanation was largely dismissed, but scientists still didn't know what caused the star's bizarre behavior. Now, reports that space dust is likely responsible for the mysterious phenomenon.

Published in the journal The Astrophysical Journal Letters [PDF], a new study of KIC 8462852's behavior "shows that different colors of light are being blocked at different intensities," said Tabetha Boyajian, an astronomer at Louisiana State University and the study's lead author, in a statement. "Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure."

KIC 8462852 sits 1500 light-years away from Earth, and is about 50 percent larger and 1000 degrees hotter than the Sun, according to scientists. It's nicknamed "Tabby's star" after Boyajian, who first observed its unusual flickering pattern in 2011 while perusing data from NASA's Kepler Space Telescope with a team of citizen scientists from the online Planet Hunters group. Boyajian and several of the group's members published a paper in 2015 that detailed KIC 8462852's waning and waxing brightness over the course of four years. The data puzzled scientists around the world.

KIC 8462852's otherwise consistent flux was interrupted by sporadic—and substantial—dips in light. Planets can cross in front of distant stars and occlude their light, but even transiting Jupiter-sized planets typically cause a dip of less than 1 percent. In KIC 8462852's case, the difference was up to 22 percent. Further adding to scientists' confusion, KIC 8462852 is an older star that isn't surrounded by the dust and debris from its formation, which can obscure a star's shine.

Theories for the star's behavior ranged from telescope malfunctions to comet fragments moving in an elliptical orbit around the star. Another hypothesis was that a dusty debris disk could be enveloping a black hole located between KIC 8462852 and Earth, National Geographic reports.

Meanwhile, Penn State astronomer Jason Wright hypothesized that alien megastructures, otherwise known as Dyson Spheres, could be harvesting energy from KIC 8462852. (This idea was swiftly debunked.)

To find some answers, Boyajian and colleagues performed follow-up research from March 2016 to December 2017 that was funded through a Kickstarter campaign that raised more than $100,000. Using ground telescopes provided by Las Cumbres Observatory in Goleta, California (and numerous volunteer telescopes around the world), they noted four additional instances in which KIC 8462852 dimmed for stretches of time ranging from days to weeks, according to Gizmodo. (Kickstarter supporters even got to name these instances.)

So far, real-time data from this new study suggests that space dust (perhaps the fragments of a recently destroyed planet or moon) is the likely answer for KIC 8462852's unusual flickering. But no conclusive results have been reached quite yet. For now, the star will continue to stymie scientists. At least they can finally eliminate the phrase "alien megastructure" from their vocabularies.