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How Scientists Discovered KIC 8462852 Is The Most Mysterious Star In The Universe!

As astronomer, Jason Wright, from Penn State University, told the Atlantic, “Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build.” So just how did the idea of Alien Megastructures surface? KIC 8462852 is also known as Tabby’s star after its discoverer Tabetha Boyajian of Yale University. What caught her attention was that KIC 8462852’s light dipped by as much as 20 % and didn’t conform to any regular time intervals which distinguish a planet.The first signs of this space oddity came from NASA’s planet-hunting Kepler space telescope looking at region between 2009 and 2013. Planet-hosting stars such as our Sun show regular dips as planets pass in front of them. Tabby’s star stood out because it dipped erratically throughout the four years of2009 and 2013, by as much as 20% of its brightness. That’s when Bradley Schaefer, at Louisiana State University in Baton Rouge, examined the star’s behaviour over the past century by looking at more than 1200 old photographic plates from 1890 to 1989 which revealed that Tabby’s star gradually dimmed by as much as 15 % during that time. However, some were skeptical of Schaefer’s work but very few astronomer could challenge it because hardly anyone can examine original photographic plates. But Schaefer had gone to Harvard to look at the original photographic plates and personally 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 on expert. “Schaefer is an expert at this stuff.”

That when a young scientist named Montet and his advisor Josh Simon realised that an answer might be hidden within the Kepler data. As New Scientist reported:
 They found that for the first 1000 days of the Kepler mission, Tabby’s star decreased in brightness at roughly 0.34 % a year – twice as fast as measured by Schaefer. What’s more, over the next 200 days, the star’s brightness dropped another 2.5 per cent before beginning to level out. It was a much more rapid change than before. That means the star undergoes three types of dimming: the deep dips that first made it famous, the relatively slow decline observed by Schaefer and verified by Montet and Simon, and the intermediate rapid decline that occurred over a few hundred days.

“We can come up with scenarios that explain one or maybe two of these, but there’s nothing that nicely explains all three,” says Montet. And the team doesn’t want to resort to creating three separate scenarios. “It would be much more satisfying to think of a single physical cause that could be responsible for all of the brightness variations that we observe,” says Simon. “But we’re still struggling to come up with what that might be.”  Explanations range from a swarm of comets orbiting the star to an intervening cloud in the interstellar medium – but none fit all the data.
It should be noted that 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.” That one reason that the alien megastructures came into the equation but Schaefer for one 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. And points out  that object like a megastructure 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.”

As New Scientist observed:
 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.”
Here the abstract from Cornell University: KIC 8462852 Faded at an Average Rate of 0.165+-0.013 Magnitudes Per Century From 1890 To 1989 by Bradley E. Schaefer

KIC8462852 is a completely-ordinary F3 main sequence star, except that the light curve from Kepler shows episodes of unique and inexplicable day-long dips with up to 20% dimming. Here, I provide a light curve of 1338 Johnson B-band magnitudes from 1890 to 1989 taken from archival photographic plates at Harvard. KIC8462852 displays a secular dimming at an average rate of 0.164+-0.013 magnitudes per century. From the early-1890s to the late-1980s, KIC8462852 faded by 0.193+-0.030 mag. The decline is not an artifact because nearby check stars have closely flat light curves. This century-long dimming is unprecedented for any F-type main sequence star. Thus the Harvard light curve provides the first confirmation (past the several dips seen in the Kepler light curve alone) that KIC8462852 has anything unusual. The century-long dimming and the day-long dips are both just extreme ends of a spectrum of timescales for unique dimming events. By Ockham’s Razor, two such unique and similar effects are very likely produced by one physical mechanism. This one mechanism does not appear as any isolated catastrophic event in the last century, but rather must be some ongoing process with continuous effects. Within the context of dust-occultation models, the century-long dimming trend requires 10^4 to 10^7 times as much dust as for the deepest Kepler dip. Within the context of the comet-family idea, the century-long dimming trend requires an estimated 648,000 giant comets (each with 200 km diameter) all orchestrated to pass in front of the star within the last century.

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