It's not looking like aliens. But could a swarm of comet fragments be responsible for the light fluctuations from Tabby's Star? © NASA/JPL/Caltech

Mystery star’s light signals probably not the result of alien activity

Astronomers cast doubt on the idea of an alien megastructure orbiting Tabby’s Star.

KIC 8462852. It’s not the catchiest name, but this star has had alien hunters getting all hot and bothered over the past few months. Now, a new study has revealed that the star’s unusual activity probably isn’t the result of little green men after all.

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Also known as Tabby’s Star, KIC 8462852 lies about 1,480 light-years away in the constellation Cygnus. The star suddenly found itself in the spotlight last autumn when a citizen science group discovered strange fluctuations in its light, detected in data from the Kepler space telescope.

The situation hit fever pitch in October when astronomers at Pennsylvania State University suggested that the flickering light signal could be explained by an alien megastructure passing in front of the star, blocking out its light.

Scientists at the SETI Institute trained the Alien Telescope Array on the star to look for telltale radio signals, to no avail. But then, in January, an astronomer at Louisiana State University calculated that the star’s brightness had dimmed by 20 per cent over the last century. This was difficult to explain by natural processes, but alien activity was a possible cause. A vast megastructure built around this star over time would have absorbed increasing amounts of energy from it, reducing its light output. Mystery solved?

Alas, it seems not. A new study by astronomers in Germany and the US calls into question the claims that the star’s brightness has decreased. Their analysis reveals that the apparent dimming is most likely an artefact of the different telescopes and cameras used to photograph the star over the past century.

“Whenever you are doing archival research that combines information from a number of different sources, there are bound to be data precision limits that you must take into account,” says Keivan Stassun, co-author of the study at Vanderbilt University in Nashville, US. “In this case, we looked at variations in the brightness of a number of comparable stars in the DASCH [Digital Access to a Sky Century @ Harvard] database and found that many of them experienced a similar drop in intensity in the 1960s. That indicates the drops were caused by changes in the instrumentation, not by changes in the stars’ brightness.”

So for now, the case of the twinkling star remains unsolved.

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

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One possible explanation is a huge comet passing by the star, fragmenting into thousands of smaller comets. Astronomers around the world are now pointing their telescopes in the star’s direction in the hope of catching more light dips and more clues to this cosmic mystery. Where’s Sherlock Holmes when you need him?