The researchers worked through every known possibility, but each solution presented a new problem. For example, they investigated the possibility of some kind of circumstellar disk of dust. However, after looking for the infrared signal associated with these disks, no such signal could be seen.
Also, the star is a mature F-type star, approximately 1.5 times the size of our sun. Circumstellar disks are usually found around young stars.
ANALYSIS: Alien 'Star Engine' Detectable in Exoplanet Data?
The researchers also investigated the possibility of a huge planetary collision: could the debris from this smashup be creating this strange signal? The likelihood of us seeing a planetary collision is extremely low. There is no evidence in data taken by NASA's Wide-field Infrared Survey Explorer (WISE) that a collision happened, creating a very tiny window of opportunity between WISE's mission end and the beginning of Kepler's mission (of a few years) for an astronomically unlikely cosmic event like this to occur.
The only natural explanation favored by the researchers seems to focus on an intervening clump of exocomets.
"One way we imagine such a barrage of comets could be triggered is by the passage of a field star through the system," write the researchers.
Indeed, they argue, there's a nearby star that might have tidally disturbed otherwise dormant comets in the outermost regions of the KIC 8462852 star system. This small star is located around 1,000 AU from KIC 8462852 and whether it's a binary partner or an interstellar visitor, its presence may have caused some cometary turmoil. Like the other scenarios, however, the exocomet explanation still falls short of being fully satisfactory.
This research paper focuses only on natural and known possible causes of the mystery transit events around KIC 8462852. A second paper is currently being drafted to investigate a completely different transit scenario that focuses around the possibility of a mega-engineering project created by an advanced alien civilization.
ANALYSIS: Our Super-Advanced Alien Neighbors are Missing
This may sound like science fiction, but our galaxy has existed for over 13 billion years, it's not such a stretch of the imagination to think that an alien civilization may be out there and evolved to the point where they can build megastructures around stars.
"Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build," Jason Wright, an astronomer from Penn State University, told The Atlantic.
Indeed, hunting down huge structures that obscure the light from stars is no new thing. The Search for Extraterrestrial Technology (SETT) is one such project that does just this. Only recently, a survey of the local universe focused on the hope of detecting the waste heat generated by a technologically advanced civilization, specifically a Type II Kardashev civilization.
On the Kardashev scale, a Type II civilization has the ability to utilize all the available energy radiating from a star. Using a vast shell or series of rings surrounding a star, a Dyson sphere-like structure may be constructed. This has the effect of blotting out the star from view in visible wavelengths, but once the solar energy has been used by the alien civilization, the energy is shifted to longer wavelengths and likely lost as infrared radiation.
ANALYSIS: Could We Detect an Alien Civilization's Waste Heat?
This recent search for aliens' waste heat drew a blank, reaching the conclusion that as there appears to be no alien intelligence cocooning stars to harvest their heat, there's likely no Type II civilization nearby.
But as KIC 8462852 is showing us, there may be something else out there - possibly an alien intelligence that is well on its way to becoming a Type II civilization, which is setting up some kind of artificial structure around its star.
Of course, these mystery transit events are nowhere near "proof" of an alien civilization. In fact, it's barely evidence and a lot more work needs to be done.
The next step is to point a radio antenna at KIC 8462852, just to see whether the system is generating any artificial radio signals that could indicate the presence of something we'd define as "intelligent." Boyajian and Wright have now teamed up with Andrew Siemion, the Director of the SETI Research Center at the University of California, Berkeley, to get a radio telescope to listen into the star and if they detect an artificial signal, they will request time on the Very Large Array (VLA) to deduce whether any radio signals from that star are the chatter of an alien civilization.
It might be a long shot, and the phenomenon is more likely a clump of comets or some other natural phenomenon that we haven't accounted for blocking star light from view, but it's worth investigating, especially if there really is some kind of alien intelligence building structures, or perhaps, ancient structures of a civilization long-gone, around a star only 1,500 light-years away from Earth.