How Astronomers Will Solve the 'Alien Megastructure' Mystery

KIC 8462852 has rapidly become one of the major astronomical mysteries of the decade. It’ll be months before we have any strong answers on this restlessly shaky star, but astrophysicists intend to get to the bottom of it. How?

“If we could catch it in the act of dimming again, that would really help,” Penn State’s Jason Wright told Gizmodo.

Wright’s the astrophysicist who made KIC 8462852 famed last fall, when he nonchalantly proposed that the star might be blocked by an alien megastructure. He, along with numerous other astrophysicists I spoke with this week, agrees that the way we’re going to figure this weird star out is to watch it doing something weird.

KIC 8462852, also known as “Tabby’s Star,” was first spotted in the Kepler Space Telescope’s dataset last September. In spite of being an ordinary, main sequence F-type star—slightly hotter and bigger than our sun—it gathered astronomers’ attention. Over four years of observational data, the star’s light output intermittently tanked, something that isn’t regular with any cosmological phenomenon we’re aware of. Clarifications for the star’s disorderly behavior ranged from a swarm of comets to gravity darkening to alien megastructures. You can visualize which of those possibilities sparked a global hysteria.

But KIC 8462852 wasn’t done astonishing us. The mystery extended last week when Louisiana State University’s Bradley Schaefer decided to look at KIC 8462852 in old photographic plates of the sky. When he did, he saw something surprising: over the past century, the star’s total light output has fallen down by about 19%. This star isn’t just sputtering—it’s fading out completely.

“Observationally, there is zero precedent for any main sequence star to vary in brightness like this,” Schaefer told Gizmodo. “Seeing this star fade by 20 per cent over a century is more than just startling.”

How Astrophysicists Will Solve the 'Alien Megastructure' Mystery

Dips in KIC 846285’s brightness over Kepler’s 1500-day observational period. The bottom two panels are blown-up versions of the top one centred around day 800 and 1500. Via Boyajian et al. 2015

“We were mystified when it was just the Kepler data, and if it were just this we’d be baffled,” Wright said. “The comet hypothesis was great since it could explain almost anything, but it doesn’t really work for the new data.”

What we do know, according to Wright, is that whatever’s blocking the star isn’t producing strongly in the infrared spectrum, meaning it isn’t very warm. That means we’re speaking about something in a distant orbit, which doesn’t increase our odds of getting a good look at it.

KIC 8462852 is fading over time. Blue diamonds signify measurements taken among 1890 and 1989, while solid and dashed lines are fitted trends. Via Schaefer 2016.

But there is one way astrophysicists can learn what’s triggering the star to sputter—and that’s to catch KIC 8462852 doing it again.

When Kepler watched KIC 8462852 flicker numerous years back, it was only gathering white light—aggregating information across the visible spectrum. All we can do with this data is locate dimming events. But if it occurred again, astrophysicists would be ready to make precise measurements in a wider range of wavelengths. As KIC 8462852's starlight passes through whatever material is blocking it, certain colors will be absorbed more than others. This gives us a spectral fingerprint, which can be used to work out what type of material we’re looking at.

“From the spectrum, we might see absorption lines from any gas related to the ‘occulter,’” Shaefer said. “We might see a reddening that would point to the occulter being mainly dust, or we might see a color neutral dip that would point to a solid body. This would significantly narrow down models.”

For the next few months, astrophysicists are sitting tight. KIC 8462852 is behind the Sun and only visible during daylight hours, making it difficult to observe from the ground. According to Tabetha Boyajian, the Yale astrophysicist who discovered the star, a few satellites are watching it, but the temporal coverage isn’t great. “Mainly, we are now using this time to prepare for what to do when the star becomes visible again in a few months,” she said.

This includes discussing different situations, and figuring out what data will be required to confirm or refute each of them. “When the dipping starts again, we will be ready to hit it with everything we have,” she said.

Wright added that though two independent surveys haven’t turned up any proof of extraterrestrial technology, UC Berkeley’s SETI program is now working with the billionaire-backed alien hunting initiative Breakthrough Listen, and plans to conduct a very sensitive broadband sweep of the star’s neighborhood in the next few months. The prospect that we’re looking at a bona fide Dyson sphere is as improbable as ever, but....well, it hasn’t been ruled out.

“The ET hypothesis has very little predicative power,” Wright said, noting that you can invoke it to explain just about anything—the so-called “aliens in the gaps” fallacy.

Nevertheless, you can bet astrophysicists won’t rest until they’re sure one way or the other.

Article originally Published on Gizmodo



KIC 8462852


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