In Schaefer’s second look at the data on Tabby’s star, he averaged the century of data from the photographic plates into 5 year bins and looked for anything odd. Sure enough, he found something else strange about this intriguing star.
An article on the New Scientist website fills in the details of what he found:
Schaefer decided this unusual star deserved a second look. He averaged the data in five-year bins to look for slow, long-term trends, and found that the star faded by about 20 per cent between 1890 and 1989. “The basic effect is small and not obvious,” he says.
To confirm the fade was real, Schaefer went to Harvard to look at the original photographic plates and inspected them by eye for changes, a skill few astronomers possess these days. “Since no one uses photographic plates any more, it’s basically a lost art,” says Wright. “Schaefer is an expert at this stuff.”
Schaefer saw the same century-long dimming in his manual readings, and calculated that it would require 648,000 comets, each 200 kilometres wide, to have passed by the star – completely implausible, he says. “The comet-family idea was reasonably put forth as the best of the proposals, even while acknowledging that they all were a poor lot,” he says. “But now we have a refutation of the idea, and indeed, of all published ideas.”
“This presents some trouble for the comet hypothesis,” says Boyajian. “We need more data through continuous monitoring to figure out what is going on.”
What about those alien megastructures? Schaefer is unconvinced. “The alien-megastructure idea runs wrong with my new observations,” he says, as he thinks even advanced aliens wouldn’t be able to build something capable of covering a fifth of a star in just a century. What’s more, such an object should radiate light absorbed from the star as heat, but the infrared signal from Tabby’s star appears normal, he says.
“I don’t know how the dimming affects the megastructure hypothesis, except that it would seem to exclude a lot of natural explanations, including comets,” says Wright. “It could be that there were just more dimming events in the past, or that astronomers were less lucky in the past and caught more dimming events in the 1980s than in the 1900s. But that seems unlikely.”
There’s no doubt KIC 8462852 is behaving strangely, so something must be responsible, says Schaefer. “Either one of our refutations has some hidden loophole, or some theorist needs to come up with some other proposal.”
So, the saga continues and the mystery deepens, stay tuned to Science Rocks My World for future developments on the mysterious “alien megastructure” star. For more details on Schaefer’s research see the excellent article on the New Scientist website.
Source: NewScientist.com – “Comets can’t explain weird ‘alien megastructure’ star after all“
Featured Image Credit: NASA/JPL
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