The bizarre dimming of the “alien megastructure” star KIC 8462852 could be caused by a Saturn-like planet with tilted ring structures surrounding it, a team of scientists has suggested.
In a study submitted to the Monthly Notices of the Royal Astronomical Society, researchers from the University of Antioquia in Colombia have a new hypothesis to explain the strange phenomenon observed over recent years. And they suggest that the presence of ringed planets could also account for other inexplicable objects in the universe.
The mystery of KIC 8462852 began in 2015 when a team of astronomers led by Tabetha Boyajian of Louisiana State University announced that the star—which is about five times brighter than our sun—had periodically experienced huge dips in its brightness. Dimming like this normally happens when objects pass in front of a star, blocking out some of its light.
But the extent and timing of the dips were unusual. Any orbiting planet would block the same amount of light at a regular interval. But the dips recorded at KIC 8462852 took place at irregular intervals, and the amount of light that was blocked varied widely—from just a few percent up to a massive 20 percent. To put that in perspective, when Jupiter passes in front of our sun, the giant planet blocks about 2 percent of its light. The darkening seen with this star was a complete anomaly for astronomers.
Many explanations have been proposed, including a huge swarm of comets that intermittently pass in front of the star, another unidentified star sitting along the same line of sight and, finally, an "alien megastructure." The latter would involve an advanced alien civilization creating a structure around the star to harness its energy.
In the latest study, researchers explore the possibility that the dimming is the result of a large, ringed exoplanet orbiting very close to KIC 8462852. The team, led by Mario Sucerquia, performed simulations of how the planet’s ring might change over time, finding that short-term changes to shape and orientation would lead to varying transits and eclipses.
“Any detected anomaly in transit characteristics may lead to a miscalculation of the system’s properties,” they wrote. “Moreover, oscillating ring-like structures may account for the strangeness of some light-curve features in already known and future discovered exoplanets.”
The authors emphasize that their findings are speculative and that they would need to observe signatures of such a ring or disc to back up their hypothesis. “If consecutive observations evidence some signatures of a damping in the observed transit depth, we could be witnessing for the first time the disruption of a moon and the [birth] of a new ringed exoplanet.” That further work is beyond the scope of the current paper, the authors note.
The cause of the dimming is still a mystery. Pennsylvania State University professor Jason Wright, who initially proposed the possibility of an alien megastructure, told Newsweek at the time, “We’re hopeful this is just the first of many, and hopefully even deeper, dips to come in the near future. But even if not, even if it’s another year, we have so much data I’m sure we’ll be able to exclude some possibilities.”
Boyajian and her colleagues continue to monitor the star for new dips in its brightness, and in May they mobilized a network of scientists to observe a flux in KIC 8462852’s luminosity. In her latest study, which has been accepted for publication in The Astrophysical Journal, researchers looked at measurements taken from KIC 8462852 between October 2015 and December 2016. Dimming was similar to what had been observed in the 1,400 previous days.
Boyajian and her co-authors attribute the dips to circumstellar material, noting that the dimming could be the result of “some dusty structure” in the Oort Cloud, a shell of icy objects that surrounds our solar system. This proposal comes with problems, however. The orbital timescale does not fit with observations and should be recurrent, the team notes. In their conclusion, they add, “Some form of circumstellar material is the most likely explanation for the long-term secular dimming.”