'Alien Megastructure' Star Not Alone. More Mysteriously Dimming Objects Found.

This artist's illustration depicts a hypothetical dust ring orbiting KIC 8462852, also known as Boyajian's Star or Tabby's Star.

(Image credit: NASA/JPL-Caltech)

A mysterious star whose repeated bouts of darkening might be due to "alien megastructures," according to some researchers' conjectures, may now have more than a dozen counterparts that display similarly mystifying behavior, a new study finds.

Further research into all of these stars might help solve the puzzle of their bewildering flickering, the study's author said.

When the researchers analyzed data from NASA's Kepler space telescope, astronomer Tabetha "Tabby" Boyajian, then at Yale University, and her colleagues found dozens of odd instances of KIC 8462852 dimming by up to 22%, with such dips lasting anywhere from a few days to a week. These events did not appear to follow any pattern and seemed far too substantial to be caused by planets or dust crossing the star's face.

These analyses of KIC 8462852 — now nicknamed "Boyajian's star" (formerly Tabby's star) after its discoverer — raised the possibility that astronomers had detected signs of intelligent alien life. Specifically, researchers have suggested that the star is surrounded by a Dyson sphere, a hypothetical megastructure that is built around a star to capture as much of its light as possible. Mathematician and physicist Freeman Dyson suggested that such megastructures could help power an advanced civilization. (Science fiction often depicts Dyson spheres as solid shells around stars, but the megastructures also could be globular swarms of giant solar panels.)

The megastructure hypothesis is near the bottom of most astronomers' lists these days when it comes to Boyajian's star, however; further analyses have pointed to more prosaic explanations, such as clouds of dust or comet fragments. Still, scientists have not yet nailed down the precise cause of the odd dimming. The answer remains elusive in part because Boyajian's star seemed unique; there were no known counterparts to provide additional clues that might help researchers solve this cosmic mystery.

Schmidt looked for counterparts of Boyajian's star using software that searched for analogous dimming events from about 14 million objects with varying brightness monitored in the Northern Sky Variable Survey from April 1999 to March 2000. He then followed up on promising candidates by examining their long-term behavior, using data from the All-Sky Automated Survey for Supernovae, ruling out sources whose dimming could be caused by conventional explanations such as an eclipsing companion star or some intrinsic variability in brightness.

Further analysis using data from the European Space Agency's Gaia space observatory found that these potential dippers tended to be either conventional "main-sequence" stars with about the same mass as the sun or red giant stars with about twice the sun's mass. The slow and rapid dippers are seen in both groups, which may suggest that they represent varying degrees of the same mechanism, Schmidt said.

Michael was a science writer for the Idaho National Laboratory and has been an intern at Wired.com, The Salinas Californian newspaper, and the SLAC National Accelerator Laboratory. He has also worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz.