KIC 8462852 is known as the "most mysterious star in the universe" for good reason. Astronomers have been baffled by the strange way its brightness fluctuates dramatically and unpredictably. That feature has led to a whole range of hypotheses about what could be happening up there—including that aliens had built a large structure around the star, as a way to harness its energy.
New monitoring of the star conducted in 2017 has now ruled out that idea, according to a new paper published today in the journal Astrophysical Journal Letters.
"It was an interesting idea to follow up on, but I don't think anyone's really upset at the claim that it is probably not what's going on," lead author Tabetha Boyajian, an astronomer at Louisiana State University, told Newsweek. (Jason Wright, the Penn State University astronomer who first suggested the alien megastructure theory, is also a co-author on the new paper.) "That was one of the very many bad ideas that we had and we couldn't really rule it out."
The new paper argues that four strange dimming episodes that took place in 2017 were likely caused by tiny dust particles surrounding the star, potentially combined with changes in the star itself. (The new monitoring also included observations of the star itself, which looked perfectly normal.)
"We don't really have a working model quite yet, so things are still up in the air in terms of how everything is put together," Boyajian said. "Where that dust is, where it's coming from, how it's generated is still very much up in the air." But the dips in brightness the authors watched this year definitely don't match what they would expect from something opaque, like an alien megastructure.
KIC 8462852 is often nicknamed Tabby's star after Boyajian, who has led its observations through the roller coaster of the past couple years. "It's been pretty overwhelming," she said of the whole experience. "When you say you don't really know what's going on, then everybody gets really excited about it."
"It's really exciting that we have all this data," Boyajian said of the 2017 observations. The team is set to observe the star again beginning in late February or early March when it reappears over the horizon, through the middle of the year. But she says that for a star this weird, that's not enough.
"I would feel a lot more comfortable if we had enough monitoring to take us through the next decade," she added. "It sounds like a lot, but with this star we can't really predict when things will happen."