No Signal from “Alien Megastructure” Around Star

An artist's conception of a disk of dust around a distant star which could periodically block or attenuate its light for external observers (credit: NASA)

An artist’s conception of a disk of dust around a distant star which could periodically block or attenuate its light for external observers (credit: NASA)

Using the Allen Telescope Array, astronomers at the SETI institute have examined the star KIC 8462852 for signs of extraterrestrial communications. So far they have come up empty. But astronomers around the world continue to examine this curious star which appears to decrease in apparent brightness by up to 20% for a period of 5 days to 80 days. Some have suggested– seriously– that the timing and magnitude of the brightness drop might be caused by a massive alien megastructure that surrounds the star.

The Allen Array was used for 12 hours a day from October 15-30, 2015 to look for signals in the 1-10 GHz range which astronomers favor for searches of extraterrestrial signals. The interstellar medium– the space between the stars– is more transparent in this range, so presumably alien civilizations who wish to send a signal in our directions would use this frequency range to communicate with us. Astronomers searched for narrowband signals that might be sent out in all directions for direct communications, and they searched for broadband signals which might be emitted by propulsion or other large engineered systems. Of course, while the SETI Institute results came back negative, if there is a civilization in the vicinity of KIC 8462852, its members may have other things on their minds other than communicating with us.

Four instances of dips in brightness of the star KIC 8462852 as observed by the Kepler Space Telescope (credit: Credit: Boyajian et. al)

Four instances of dips in brightness of the star KIC 8462852 as observed by the Kepler Space Telescope (credit: Boyajian et. al)

Or there could be– and very likely is– an explanation of the strange light curve of KIC 8462852 that does not involve alien megastructures. Some astronomers have suggested a cloud of comets surrounding the star may periodically block some of the star’s light. Or there could be an immense cloud of fine dust from a shattered comet. Astronomers are keenly watching for the next drop in brightness from the star. If they can catch it in the act, and if they can analyze how different colors of light are attenuated, they may gain more insight into what’s causing the bizarre drop in brightness. If, for example, ultraviolet and blue light are attenuated more than red and infrared light, the will have a strong hint that dust or gas may be involved rather than a solid structure. The dips in brightness were observed several times in the past few years by the Kepler Space Telescope, so we may not need to wait for long for this mystery to be solved.

Artist's image of a Dyson Sphere, an engineered alien megastructure to harness the energy of a stars (from: http://larryniven.wikia.com/wiki/Dyson_sphere)

Artist’s image of a Dyson Sphere, an engineered alien megastructure to harness the energy of a stars (from: http://larryniven.wikia.com/wiki/Dyson_sphere)

KIC 8462852 is a large star of spectral type F3 IV/V, which means its about 50% larger and slightly hotter than our Sun and just starting to run low on hydrogen fuel in its core. The stars is about 1,500 light years away and appears in the constellation Cygnus about halfway between brilliant Deneb and the star δ Cygni (Rukh) at the tip of the western wing of the celestial swan. It shines at 11th magnitude and is well within reach of a small telescope.

 

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