Mysterious ‘Alien Megastructure’ Star is Even Stranger Than Scientists Thought

Scientists found themselves--yet again--raising their eyebrows at the mysterious star known as KIC 8462862 or the "alien megastructure" star.

Newly analyzed observations from NASA's Kepler space telescope found that the star, which has since been known for its constant dips in luminosity, have been actually dimming during the four years it had been under the telescope's observation.

"The steady brightness change in KIC 8462852 is pretty astounding," Ben Montet from the California Institute of Technology (Caltech) in Pasadena and co-author of the new study, said in a news release. "Our highly accurate measurements over four years demonstrate that the star really is getting fainter with time. It is unprecedented for this type of star to slowly fade for years, and we don't see anything else like it in the Kepler data."

The "alien megastructure" star, which is unofficially named Tabby's star after astronomer Tabetha Boyajian of Yale University who discovered the star's diminishing light, has become famous among the scientific community when it was suspected that the flickering signals from the star were a result of an alien megastructure.

Further observations found no alien megastructure of any kind, which led scientists to speculate other possibilities, such as a cloud of dust and fragments from a comet or planet periodically blocking the star's light or an unknown object between the star and the Earth.

In January, a controversial study by astronomer Bradley Schaefer of Louisiana State University claimed that Tabby's star have dimmed overall by 14 percent from 1890 to 1989. This prompted Montet and co-author Joshua Simon from the Carnegie Institution of Washington to investigate the behavior of the star. They introduced their findings in August when they posted a preprint version of the paper while the actual paper was being reviewed. Now, their work has been accepted for publication by The Astrophysical Journal.

Using Kepler calibration images, they found that over the first three years of the Kepler mission, the star had dimmed by almost 1 percent. In just over six months, the brightness again dropped by 2 percent, staying dim throughout the final six months of the mission.

The researchers compared Tabby's star with over 500 similar stars observed by Kepler. While they found that a small number of stars exhibited the same dimming as seen in Tabby's star during the first three years of Kepler images, none of them showed such a dramatic decrease in brightness in just six months or an overall change in brightness of 3 percent.

Montet and Simon proposed that the dimming might be caused by a collision or breakup of a planet or comet in the star's system, creating a fleeting cloud of dust and debris that blocked the starlight. But according to the researchers, this could not explain the long-term dimming of the star during the first three years of Kepler observation.

"It's a big challenge to come up with a good explanation for a star doing three different things that have never been seen before," Monet said. "But these observations will provide an important clue to solving the mystery of KIC 8462852."