Lingam and Loeb offered a provocative solution to the puzzle: Maybe some of the FRBs are artificial. If that were the case, what would be the purpose of such incredibly powerful bursts? In a 2017 paper in Astrophysical Journal Letters, Lingam and Loeb raise two possibilities: It could be a beacon to broadcast the presence of an alien civilization, which they deem “rather implausible.” Or, it could power large spaceships tugged by even larger (in area, not in mass) light sails. “The optimal frequency for powering the light sail is shown to be similar to the detected FRB frequencies,” they write — a fact that, when combined with other technical arguments, could “lend some credence to the possibility that FRBs might be artificial in origin.”
Naysayers might dismiss this, insisting that “extraordinary claims require extraordinary evidence,” Loeb notes. “I say that they require evidence, but why should they be held to a higher plane? We should not automatically dismiss explanations just because they seem exotic to some people.”
Searching for artifacts
“When exploring habitable worlds around other stars, we might … find planets with burnt-up surfaces, abandoned mega-structures or planetary atmospheres rich with poisonous gases and no sign of life,” Loeb has written. One might also see an extensive network of unnatural platforms or satellites orbiting another star — perhaps part of a hypothetical energy-gathering enclosure called a Dyson sphere.
Something like this, if sufficiently large, could be spotted by NASA’s Transiting Exoplanet Survey Satellite (TESS), which looks for dips in the brightness of a star caused by a planet passing in front of it. TESS could also detect dips caused by the passage of giant artificial mega-structures. Officials announced in October 2019 that TESS would collaborate with Breakthrough Listen — a $100 million SETI initiative, the largest and most generously funded in the field’s history.
Listen’s ground-based telescopes would focus on potentially habitable planets identified by TESS. Loeb cites the example of Tabby’s Star: Discovered in 2016, two years before the TESS launch, it exhibited a peculiar dimming pattern, prompting some to speculate that it was surrounded by some kind of alien structure. It turns out that our view was blocked by an oddly shaped disk of dust, Loeb says, but that’s the kind of irregularity TESS scientists would be looking for.
Searching for interstellar visitors
On Oct. 19, 2017, an astronomer using Hawaii’s Pan-STARRS telescope discovered an object moving past the sun at 196,000 miles per hour (315,431 km/hr), so fast that it almost surely originated from outside the solar system. The object, dubbed ‘Oumuamua — Hawaiian for “first scout from a distant place” — was initially classified as an asteroid and then a comet and more recently as a chunk of hydrogen ice.