Dust, Not an Alien Megastructure, Likely Causes Strange Winks in Tabby’s Star Brightness

After extensive observations, researchers can now confidently say: It’s not aliens

Artist's illustration of Tabby's Star, also known as KIC 8462852. NASA/JPL-Caltech

After two years of intensive observations and sometimes wild theories, astronomers are confident in saying that the secret of Tabby’s star’s mysterious dips in light is not due to alien megastructures.

The star KIC 8462852 is nicknamed “Tabby’s star” in tribute to astronomer Tabetha Boyajian, whose team first identified the star’s unusual behavior in 2015. The otherwise-normal star sits 1,500 light-years from Earth but sporadically dims and brightens. The star is brighter than our sun, Mike Wall reports for Space.com, but experiences some drastic dips in brightness—once even dimming up to 22 percent of its usual luminosity.

This inexplicable behavior set off a storm of curiosity. What could drive the irregular brightness? Many possibilities have been suggested, including everything from swarms of shattered comets to black holes, reports Nadia Drake for National Geographic. The most spectacular suggestion, however, was that the dips were the result of an orbiting alien megastructure—a swarm supposedly engineered to collect energy for a distant civilization.

This remote possibility of finding life beyond our own was enough to spark widespread public interest. A Kickstarter campaign quickly raised over $100,000 to get time on ground-based telescopes to extensively observe the star, which allowed the research to progress independent of the usual funding routes and lengthy grant timelines. "Without the public support for this dedicated observing run, we would not have this large amount of data," Boyajian says in a press release.

This crowdfunded observations echos how the star's unusual behavior was identified—by enthusiastic amateurs combing through Kepler space telescope data alongside expert researchers, seeking any interesting anomalies.

The money bought time on the Las Cumbres Observatory from March 2016 to December 2017, a robotic telescope network that switches observations between 21 telescopes at eight locations as the sun rises and sets, reports Ashley Strickland at CNN. Starting in May, the observatory caught four distinct dimming events. In tribute to the research’s unorthodox funding path, crowdfunding supporters were able to name the dimming events where the star’s light dipped below usual levels.

"We were hoping that once we finally caught a dip happening in real time we could see if the dips were the same depth at all wavelengths,” astronomer Jason Wright says in a statement. “If they were nearly the same, this would suggest that the cause was something opaque, like an orbiting disk, planet, or star, or even large structures in space."

Instead, Wright and his team found some colors of light dimmed more than others, suggesting that whatever blocks the light from Tabby’s star is not a solid structure like a planet, another star, or even an alien megastructure. 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.

But there's still more for researchers to learn, reports Ben Guarino at Washington Post. The biggest question is how that dust formed—is it left from the early solar system, was it created by shattered comets or ground planets, or was it something else entirely? As researcher Tyler Ellis tells Guarino, “We are certainly not done with this star yet.”