In a recently published paper in The Astrophysical Journal Letters, Manasvi Lingam and Abraham Loeb, from the Harvard Center for Astrophysics, propose a rather intriguing explanation for the phenomena known as Fast Radio Bursts (FRBs). FRBs are very powerful and very short bursts of radio waves, originating, as far as is known, galaxies other than our own. FRBs last for only a few milliseconds, but, during that interval, they shine with the power of millions of suns.
The origin of FRBs remains a mystery. Although they were first detected in 2007, in archived data taken in 2001, and a number of FRBs was observed since then, no clear explanation of the phenomenon was yet found. They could be emitted by supermassive neutron stars, or they could be the result of massive stellar flares, millions of times larger than anything observed in our Sun. All of these explanations, however, remain speculative, as they fail to fully account for the data and to explain the exact mechanisms that generate this massive bursts of energy.
The rather puzzling, and possibly far-fetched, explanation proposed by Lingam and Loeb, is that these short-lived, intense, pulses of radio waves can be artificial radio beams, used by advanced civilizations to power light sail starships.
Light sail starships have been discussed as one technology that could possibly be used to send missions to other stars. A light sail, attached to a starship, deploys into space, and is accelerated using energy in the sending planet by powerful light source, like a laser. Existing proposals are based on the idea of using very small starships, possibly weighting only a few grams, which could be accelerated by pointing a powerful laser at them. Such a starship could be accelerated to a significant fraction of the speed of light in only a few days, using a sufficiently powerful laser, and could reach the nearest stars in only a few decades.
In their article, Lingam and Loeb discuss the rather intriguing idea that FRBs can be the flashes caused by such a technology, used by other civilizations to power their light sail spaceships. By analyzing the characteristics of the bursts, they conclude that these civilizations would have to use massive amounts of energy to produce these pulses, used to power starships with many thousands of tons. The characteristics of the bursts are, according to computations performed by the authors, compatible with an origin in a planet with a size approximately the size of the Earth.
The authors use the available data, to compute an expected number of FRB-enabled civilizations in the galaxy, under the assumption that such a technology is widespread throughout the universe. The reach the conclusion that a few thousands of this type of civilizations in our galaxy would account for the expected frequency of observed FRBs. Needless to say, a vast number of assumptions is used here to reach such a conclusion, which is, they point out, consistent with the values one reaches by using Drake’s equation with optimistic parameters.
Image source: ESO. Available at Wikimedia Commons.