"Alien-megastructure" star gets even more bizarre

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The strange dips in light from KIC 8462852 could be partially explained by the transit of debris caused by a planetary collision(Credit: NASA/JPL-Caltech)

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The star at the heart of the "alien megastructure" controversy that gripped the internet in 2015, has been observed to dim dramatically over a period of just four years according to a new study making use of data collected by NASA's Kepler spacecraft. This newest revelation will force astronomers to rethink some of the leading theories attempting to account for the enigmatic behavior exhibited by the imaginatively named star KIC 8462852.

KIC 8462852 was made famous in 2015 when a scientific paper suggested that a vast alien megastructure could have been responsible for temporary dips in the luminosity of the star that were recorded by Kepler first in 2011, and then again in 2013.

Such was the interest generated by the find, that SETI directed its powerful Allen Telescope Array to listen for signs of intelligent life beaming out from KIC 8462852. Inevitably, SETI's efforts turned up no proof of the advanced civilization purported to have created the occulting structures.

More reasonable minds suggested that the dips in light could have been created by a huge family of transiting comets passing across the disk of the star, or even the passage of debris created through a collision between two planetary bodies. As of yet, astronomers are uncertain as to what is creating the sporadic dips in light.

The new study authored by Josh Simon from the Carnegie Institution for Science, and Ben Montet of the California Institute of Technology, focused on an analysis of the light signature of KIC 8462852 as seen in calibration images captured by Kepler over the first three years of its mission.

Simon and Montet were hoping to shed light on whether the star's luminosity was diminishing with time, as had been suggested in a previous study, and to hopefully gain insights regarding the short-term occultations that had led to the initial hypothesis of an alien megastructure.

A graph displaying the luminosity of KIC 8462852 over the course of the Kepler observations(Credit: Ben Montet)

The duo discovered that, over the first three years of Kepler's primary mission, which ran from May 2009 to early 2013, KIC 8462852 dimmed by around one percent. The star's recorded brightness was then observed to decrease by a further two percent over the next six months, and was noted to remain at this diminished level for the remainder of Kepler's mission.

The light signature of KIC 8462852 was then compared to 500 other similar stars captured by Kepler. It was found that a small fraction of the stellar bodies exhibited a dimming in line with that experienced by KIC 8462852 over the first three years of Kepler observations. However, none of these stars exhibited a sudden two-percent drop in luminosity over a six-month period.

The confirmation of the gradual, and then more sudden dimming of KIC 8462852 will set it further apart from other stars of its type. According to Simon and Montet, the most likely cause of the sudden two-percent dimming of the star would be the transit of a massive dust cloud created by a planetary collision or a gigantic comet.

However, while this would explain the sudden dip, it would not account for the one-percent drop in light observed in the three years prior to the event, or the longer-term dimming suggested by the earlier (though possibly flawed) study. A new hypothesis must now be put forward to account for the strange behavior of what is arguably one of the weirdest stars discovered to date.

A paper on the discovery has been accepted for publication in The Astrophysical Journal.

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