You have probably heard of the intriguing discovery made in October 2015, when a group of astronomers detected a so-called ‘alien megastructure’ around KIC 8462852, also known as Tabby’s star.
In essence, it was a weird pattern of light which was nothing scientists had ever seen before. Normally, a star’s brightness dips by approximately 1% when a planet passes in front of it, but in the case of KIC 8462852, it was almost 22%, which suggests that there must be a really huge object nearby, which is interfering with the star’s brightness.
Second Alien Megastructure
It seems that after all, KIC 8462852 is not the only star with this kind of dimming and ‘alien megastructures’ could be more common than we thought. EPIC 204278916, detected by NASA’s Kepler spacecraft back in 2014, has a similar size to our Sun but only half its mass. For these two years, the star has been observed by a team of astronomers led by Simone Scaringi of the Max Planck Institute for Extraterrestrial Physics in Germany. As a result, they discovered something even weirder than the patterns of light exhibited by KIC 8462852.
The researchers report that the star has been showing dips in brightness of up to 65% for 25 consecutive days! What kind of space object could possibly cause this kind of dimming, considering the fact that even something as massive as a planet affects a star’s brightness by only 1%?
Since the discovery of the first ‘alien megastructure’ in 2014, the researchers have come up with three theories that could explain these weird patterns of light observed around KIC 8462852.
The first one claims that the dimming could have been caused by vast swarms of comets around the star.
According to the second theory, KIC 8462852 spins so fast that it becomes ‘oblate,’ i.e. its radius is greater at the equator than it is at the poles. As a result, the poles seem hotter and brighter than the equator, which appears to be darkened to the observer.
The third explanation, which is the least plausible of the three, suggests that there could be something similar to the Dyson Sphere we have seen in a few sci-fi movies and books. This would be a massive construction of solar panels encircling a star – an object that would be perfectly described with the term ‘alien megastructure’.
Since 2014, none of these theories has received any evidence. Now, the team of German astronomers who made the observations of EPIC 204278916 came up with a new hypothesis that could shed some light on the nature of this mysterious dimming. They say that a dust disk could be responsible for these huge dips in the light curve of the star. If the disk is oriented “edge-on” to Earth, then it could be blocking light from the star and, at the same time, interfere with our observations since we wouldn’t be able to see its infrared radiation at this angle. A fact that favors this theory is the star’s age – EPIC 204278916 is only 11 million year old, so the presence of a protoplanetary disk around such a young star makes perfect sense.
As for the age of KIC 8462852, there is no consensus among astronomers. According to the initial estimates, the star’s age is hundreds of millions of years. However, a number of astronomers tend to think that it’s as young as EPIC 204278916. But even if KIC 8462852 is much older than that, the inexplicable dimming could be caused by rings of ‘cometary-like debris’ also referred to as circumstellar disks, which many mature stars are known to have.
Whatever it is, a disk of space dust or a gigantic structure built by an advanced alien civilization, the time will show. Next year, Kepler is going to make new observations of EPIC 204278916 and who knows what else will be found in that distant corner of the universe.
Image credit: public domain art by CapnHack, via http://energyphysics.wikispaces.com/Proto-Dyson+Sphere