Turns out, it’s probably not a vast, orbiting alien megastructure that causes distant star KIC 8462852 to dim and brighten sporadically - it’s more likely just dust.
That’s the view of a new paper by Louisiana State University astronomer Tabetha Boyajian and scores of co-authors - including astronomers Brett Morris and James Davenport from the University of Washington. The paper has been accepted for publication in Astrophysical Journal Letters.
KIC 8462852 is nicknamed "Tabby’s Star” after Boyajian, who discovered it with the help of citizen scientists. The star has intrigued astronomers with its irregular, unexplained dips in light of up to about 22 percent. It’s an otherwise average star, about 1,250 light-years away, in the constellation Cygnus, and is about 40 percent more massive than the sun and about four times brighter.
The unusual dimming spawned many creative theories to explain the star’s behavior, with some hoping against all odds that the star might be orbited by a massive superstructure to harness energy -- the work of an advanced civilization. But observations from March 2016 to December 2017 from the Las Cumbres Observatory , a network of robotic telescopes, indicate the explanation is likely more prosaic than that: Space dust.
"Dust is most likely the reason why the star’s light appears to dim and brighten,” said Boyajian, an assistant professor of astronomy and physics at LSU. "The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure.”
In May of 2017, Boyajian saw that the star was again beginning to dim, and issued a call to fellow researchers to observe the star immediately. That’s where Morris and Davenport came in.
"Our involvement in this project was to be immediate responders,” said Morris, who is a UW doctoral student in astronomy. "I frequently observe on the ARC 3.5 m Telescope at Apache Point Observatory, and was able to secure a bit of time to observe at the beginning of several dips.”
Davenport, who is a post-doctoral researcher at both the UW and Western Washington University, alerted Morris to Boyajian’s call to action. Morris said he "pleaded” with those scheduled to use the telescope that late that night to get a few minutes of observing time. "At first maybe they thought I was an over-enthusiastic graduate student or a conspiracy theorist,” he said, but when he explained to them the importance of the moment, they agreed.
"Our observations were within the first three high-resolution spectra to be taken of the star after the dimming began,” Morris said. He spent the morning posting the images to Twitter , where, he said, "many open science conversations ensued.” Boyajian proudly showed Twitter followers their first response in a tweet proclaiming "Day-tah!”
Davenport, who did separate research on Tabby’s Star in late 2017 and was among those who Boyajian notified, said his contribution was mostly alerting Morris, whose expertise in observational astronomy made him "the perfect person for doing the follow-up.” Davenport also assisted in analyzing data.
"Tabby’s Star” was first seen to perform its dips by the Kepler Space Telescope in 2015. Davenport noted that more than a year passed before the anomalies in the data were noticed. "We may go back and find that this kind of event is occurring in lots of our data,” he said.
Boyajian praised the citizen scientists and Planet Hunters, who were the ones to detect the star’s unusual behavior in first place.
"If it wasn’t for people with an unbiased look on our universe, this unusual star would have been overlooked,” she said, adding. "Without the public support for this dedicated observing run, we would not have this large amount of data.”