A couple of scientists have considered how the search for extraterrestrial intelligence is conducted and, working off the idea that sufficiently advanced alien beings would at least attempt to build defensive structures around their world to defend against potentially catastrophic extraplanetary threats, suggest that one way such beings might be found would be through their defense systems. In fact, the scientists contend, the aliens would not necessarily have to be much more advanced than humans.
Inverse reported recently that Milan Cirkovic and Branislav Vukotic of the Astronomical Observatory of Belgrade have suggested in a study that searching for defensive structures that guard against something as devastating as a nearby (exploding) dying star could potentially lead to the discovery of intelligent alien beings. The duo posits that intelligent beings not much more advanced than humanity could erect artificial barriers or perhaps some type of megastructure to thwart an incoming threat like a gamma-ray blast or the expended electromagnetic energy of an exploding supernova.
Cirkovic and Vukotic write in the paper (per Business Insider), "For the present purposes, we note that no part of any spiral galaxy [like our Milky Way] can be considered safe from cosmic explosions in the long run. And as the timeframe considered by an intelligent species grows longer, more relevant becomes the issue of mitigation."
Such mitigation would include planetary defense systems, something that our own planet has yet to develop but, Cirkovic and Vukotic believe, is well within humanity's technological reach within the next century. An alien civilization just a few decades or more technologically advanced might have thought of and created such forms of mitigation already.
Such defense systems could be found much the same way as exoplanets are detected, by studying and recording the dimming of stars, a method known as transiting. The scientists suggest that there are observables to look for that could distinguish what they refer to as "shielding swarms" (like asteroids) from exoplanets: The mass of the shield construct would be the size of a planet with a great deal less mass than it should have; the structure will not obey the natural laws of motion; unusual optical properties (like infra-red absorption); and anomalous planetary reactions within a system affected by a supernova (derived from historical data).
As Inverse pointed out, the discovery of the mysterious dimming star, KIC 8462852, had scientists speculating that the effect could be caused by mitigating phenomena like planets, swarms of comets, and even a Dyson sphere (a theoretical artificial construct that would surround a star and harness its energy). And the Inquisitr reported in September that the latest theory behind the dimming was that the star was being occluded by an interstellar band of space rock and debris.
The Cirkovic and Vukotic paper appears to be an extension of the alien megastructure idea, that where one might find something resembling an artificial formation -- whether it be a manufactured sphere or a shield of unnaturally aligned asteroids -- that could be used as a defense, one might just find a nearby intelligent alien civilization.
If nothing else, the paper, which was published in Acta Astronautica, provides yet another method, along with the current searches for extraterrestrial transmissions and tell-tale atmospheric biosignatures, for detecting extraterrestrial intelligence.
Of course, the search for extraterrestrial intelligence has been going on for centuries, but the formalized and collective push to find intelligence came about when Dr. Frank Drake, the scientist that formulated the now famous Drake Equation for calculating the number of extant alien civilizations capable to extraplanetary communication within the Milky Way, pointed a radio telescope from the Greenbank Observatory in West Virginia at the distant stars stars Tau Ceti and Epsilon Eridani. His efforts, along with contributions from thousands of others, morphed into what would become SETI and the SETI Institute, the mission of which is to continue the search for alien extra-solar intelligence.
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