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Dyson sphere megastructure
An artist’s representation shows a crumbling megastructure known as a Dyson sphere orbiting KIC 8462852. (Credit: Danielle Futselaar / SETI International)

He’s not saying it’s aliens – but an astronomer has raised new questions about KIC 8462852, the strange star that stirred up a debate about “alien megastructures” months ago.

In a paper submitted to Astrophysical Journal Letters, Lousiana State University’s Bradley Schaefer reviews archival photographic plates that show KIC 8462852 at various times going back to 1890. He reports that the star, which is 1,500 light-years away in the constellation Cygnus, faded by about 20 percent between the 1890s and the 1980s.

“This century-long dimming is completely unprecedented for any F-type main sequence star,” Schaefer writes.

KIC 8462852’s dimming was already worthy of note, due to observations by NASA’s Kepler space telescope that revealed unusual episodes during which the star faded by as much as 20 percent. That led Penn State astronomer Jason Wright to observe that such a pattern was consistent with what you’d expect if aliens were building an energy-generating megastructure known as a “Dyson sphere” around the star.

Wright’s speculation touched off a flurry of reports, as well as close reviews of data from the Allen Telescope Array and NASA’s Spitzer Space Telescope. Those reviews found nothing out of the ordinary. Most astronomers came around to the view that KIC 8462852’s dimming was the result of cometary swarms that swept past the star, temporarily obscuring its light.

Schaefer, however, argues that the century-long dimming and the more recent anomalous episodes were most likely to have been caused 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,” he writes.

So what could it be? Aliens are still one of the least likely explanations, but a more sedate debate over KIC 8462852 is likely to continue for quite some time. Even before Schaefer’s paper came to light, Centauri Dreams’ Paul Gilster raised the possibility that “we’re seeing a natural phenomenon we can’t yet identify.”

Wow Signal
Astronomer Jerry Ehman scribbled the word “Wow!” next to red-circled radio readings in 1977. (Credit: Ohio State University Radio Observatory / North American Astrophysical Observatory)

‘Wow’ Signal explained?

Speaking of astronomical anomalies and comets, another study to be published by the Washington Academy of Sciences suggests that one of the best-known anomalies in SETI lore could have been caused by a pair of comets.

The anomalous 72-second radio emission, now renowned as the “Wow” Signal, was picked up in 1977 by the Ohio State University Radio Observatory (a.k.a. the Big Ear). The signal was so out of the ordinary that astronomer Jerry Ehman wrote the word “Wow!” beside the readings.

Astronomers looked for a natural explanation and came up short. But the new study, written by St. Petersburg College’s Antonio Paris and Evan Davies of the Explorers Club, says the signal could have been generated by cometary clouds of hydrogen.

Paris and Davies point to two comets in particular, known as 266P/Christensen and P/2008 Y2 (Gibbs).

Astronomers didn’t know those comets existed back in 1977, but after their discovery in 2006 and 2008, they could trace their orbital paths backward. It turns out the comets were passing through the area being monitored by the now-defunct Big Ear when the “Wow” Signal was detected.

Paris and Davies note that the comets are on track to return to the “Wow” Signal’s celestial neighborhood in 2017 and 2018.

“During this period, the astronomical community will have an opportunity to direct radio telescopes toward this phenomenon, analyze the hydrogen spectra of these two comets, and test the authors’ hypothesis,” they write.

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