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Studies pour cold water on idea of alien megastructures around a distant star

Comets and changes in telescopes offered up as explanation for star's dimming brightness.

PUBLISHED : Thursday, 12 May, 2016, 8:22pm
UPDATED : Friday, 13 May, 2016, 12:51pm

A new study adds fuel to the fiery debate raging between astronomers about a possible alien megastructure built around a star 1,480 light-years away.

In case you missed it, the star, KIC 8462852 (otherwise known as Tabby), has been causing a stir since last October, when a team of astronomers suggested the faint possibility that the strange dips they'd observed in the star's brightness could be attributed to extraterrestrial life.

This latest paper lends some support to a study which originally discredited the alien megastructure idea. That study suggested that comets, not aliens, were responsible for the eerie dimming.

A Dyson swarm

Yale astronomer Tabby Boyajianand, Penn State astronomer Jason Wright and colleagues posted their paper about KIC 8462852 on April 14, 2015. The paper was published on arXiv, an online archive where researchers can submit scientific papers without being peer reviewed.

It found uneven dips in the brightness of the star based on observations from citizen scientists. This suggested that irregularly shaped objects passing across the face of the star were temporarily blocking some of its light.

The scientists put forward several explanations for this observation, but one from Wright stuck out. He suggested that an intelligent alien civilization could be in the process of building an enormous shell of megastructures around the star as a means of harvesting its energy. The hypothetical collection of constructs is known as a Dyson swarm. 

Since then, scientists have been scrambling to make sense of these strange findings.

Scientists at SETI (Search for Extraterrestrial Intelligence) International — not to be confused with the SETI Institute — who were investigating the star found the star system to be awfully quiet with no unnatural signals coming from it.

They offered a new explanation: a giant swarm of comets passing in front of the sun produced the fluctuations of light.

But in January, a study released by Louisiana State University astronomer Bradley Schaefer said the comet explanation didn't work because Tabby's star had steadily dimmed over the last century by as much as 20 per cent.

That sort of dimming would require some 648,000 giant comets, Schaefer estimated. Not very likely. Alas, the alien megastructure idea re-emerged.

Another twist in the plot

But another new paper has found a problem with Schaefer's data: It relied on information from a bunch of different instruments. And that alone could explain the 20 per cent dip in brightness he measured, these researchers say.

For their latest study, two research teams took a look at the brightness of other stars like Tabby’s star, and they found that during the same period, their brightnesses dimmed too. Tabby was not alone.

And this dimming, they concluded, was simply the result of a change of telescopes that happened around 1962.

The new results also give some new support to the comet hypothesis, since they suggest that only 36 comets are needed explain the dips in brightness (a much more reasonable number than the 648,000 figure that Schaefer proposed in January).

Aliens or not, Tabby's star remains "the most mysterious star in the universe" as Boyajian said in a TED talk.