Results of a new study in the Astrophysical Journal (arXiv.org preprint) make it far less likely that KIC 8462852 is the home star of an advanced alien civilization which is gradually enclosing it in a Dyson sphere.

KIC 8462852, otherwise known as TYC 3162-665-1, is a main-sequence F-type star located in the constellation Cygnus, approximately 1,480 light-years away.

NASA’s Kepler Space Telescope had monitored this star for several years, observing unusual incidents in 2011 and 2013, when the star’s light dimmed in never-before-seen ways.

The star had deep dips in brightness – up to 22%, indicating that a large number of objects had passed across the star’s disk and temporarily blocked some of the light coming from it.

In October 2015, a team of astronomers at Pennsylvania State University released a preprint paper that cited KIC 8462852’s light curve as ‘consistent with’ a swarm of alien megastructures.

The attention caused astronomers at the SETI Institute to train their Alien Telescope Array on KIC 8462852 to see if they could detect any radio signals indicating the presence of an alien civilization. In November 2015 the team reported finding ‘no evidence’ of signals with an artificial origin.

Then a study released in January 2016 by Dr. Bradley Schaefer from Louisiana State University threw even more fuel on the fire of alien speculation by announcing that the brightness of KIC 8462852 had dimmed by 20% over the last century.

However, the new study, led by German astronomer Michael Hippke, has taken a detailed look at the observations on which the study by Dr. Schaefer was based and concluded there is no credible evidence that the brightness of the star been steadily changing over this period.

“We looked at variations in the brightness of a number of comparable stars in the Digital Access to a Sky Century at Harvard (DASCH) database and found that many of them experienced a similar drop in intensity in the 1960’s,” said co-author Prof. Keivan Stassun of Vanderbilt University.

“That indicates the drops were caused by changes in the instrumentation not by changes in the stars’ brightness.”

“Even if aliens are not involved, KIC 8462852 remains the most mysterious star in the Universe,” said Dr. Tabetha Boyajian of Yale University, who was not involved in the current study.

“It would take an object 1,000 times the area of the Earth transiting the distant star to produce such a dramatic effect.”

The team considered a number of possible explanations, including variations in the KIC 8462852’s output, the aftermath of an Earth/Moon type planetary collision, interstellar clumps of dust passing between the star and earth, and some kind of disruption by the star’s apparent dwarf companion. However, none of their scenarios could explain all of the observations.

Their best explanation was a giant comet that fragmented into a cascade of thousands of smaller comets.

“What does this mean for the mystery? Are there no aliens after all? Probably not! Still, the dips found by Kepler are real. Something seems to be transiting in front of this star and we still have no idea what it is,” Hippke said.

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Michael Hippke et al. 2016. A statistical analysis of the accuracy of the digitized magnitudes of photometric plates on the time scale of decades with an application to the century-long light curve of KIC 8462852. ApJ 825, 73; doi: 10.3847/0004-637X/825/1/73