Alien Megastructures, or Orbiting Dust?
October 26, 2015
The space telescope Kepler (Credit: NASA/Kepler mission/Wendy Stenzel)
We’re not saying it’s aliens…but it could be aliens. Astronomers Tabitha Boyajian and colleagues published a paper in the Monthly Notices of the Royal Astronomical Society in which they describe a star that was found to dim in a mysterious fashion over the course of their study. The star, named KIC 8462852, is 1,400 light-years from Earth. A light-year is the distance light can travel in one year, about 5.88 trillion miles (9.46 trillion kilometers).
Why is this star so puzzling to astronomers? Stars can vary in brightness slightly over time. Such objects as planets can pass in front of stars, in an event called a transit, reducing the light visible to an observer. Astronomers can use telescopes to detect such dimming, helping them to find planets orbiting distant stars. In fact, the space telescope Kepler was observing KIC 8462852 for that very reason. But the star dimmed by as much as 20 percent, far more than what would be expected from the transit of even the largest planet. Furthermore, the dimming was not regular and periodic, as would be expected from the transit of an orbiting planet. A protoplanetary disk (a disk of dense gas circling around a young star) could cause such significant dimming. But KIC 8462852 is a mature star, so any disk that once revolved around it should have formed planets and other orbiting bodies by now.
So, what explanations are left? Boyajian and her colleagues propose that an orbiting cloud of dust from an exocomet (a comet outside the solar system) is the most likely explanation. But others have weighed in as well. Some scientists have suggested that the star could be spinning very rapidly, causing it to become stretched and producing strange dips in brightness. Others suggested that dust and debris from a major collision between two planets could be the culprit.
A few scientists and others note that alien technology cannot yet be ruled out as a cause of the dip. They propose that an advanced alien civilization could be building huge groups of solar panels or other gigantic structures around the star. These structures would presumably be built to supply the enormous energy needs of such an advanced civilization. Such huge buildings, termed megastructures, could block out a portion of the star’s light to observers on Earth.
Now, telescopes all over the world—and in space—are trained on KIC 8462852. The next time the star dims, astronomers will be able to better track the dimming to reveal its cause. The Allen Telescope Array has focused in on the system, looking for characteristic radio transmissions that should “leak” from any advanced civilization. Soon, scientists should know more about this mysterious star. The odds that the star’s light is being blocked by alien megastructures are extremely small. But aliens or no, the unusual KIC 8462852 will help astronomers learn more about the nature of star systems.
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