Search for ET switches to lasers
Could photonics provide the breakthrough for alien hunters? Andrew Masterson reports.
An intricate series of photographs of the Andromeda galaxy is set to be used as a test case to search for extra-terrestrial civilisations that are using optical beams to send a signal.
The photographs, currently being taken by the robotically controlled Las Cumbres Observatory, a network of 21 telescopes dotted around the planet, have been commissioned by University of California experimental cosmologist Philip Lubin as part of a project known as the Trillion Planet Survey.
The theory behind the imaging marks an interesting change – or, at least, extension – of methods currently used in the ongoing search for extra-terrestrial life (SETI). For a long time, the search has concentrated on looking for radio signals. Currently, the SETI Institute – the primary organisation concerned with looking for ET – is also developing a system to search for possible alien laser flashes, but Lubin’s team is exploring a different approach.
Lubin and colleagues are taking a lead from recent advances in the field of photonics – in particular, work on creating reliable “directed energy” applications using a combination of lasers. While certain technical challenges remain, directed energy is a high priority research field for the US navy, which is developing its own laser weapon system.
Lubin himself is very active in the field. For his Trillion Stars Survey project, the single most attractive quality of a directed energy beam is that it is bright – very, very, very bright.
“For very narrow linewidth lasers,” he wrote in a 2016 paper, “the laser can be nearly as bright as the sum of all stars in the universe within the linewidth. Even modest directed energy systems can stand out as the brightest objects in the universe within the laser linewidth.”
This, clearly, should make them pretty easy to spot. The reasoning, however, rests in a couple of caveats.
“First and foremost, we are assuming there is a civilisation out there of similar or higher class than ours trying to broadcast their presence using an optical beam,” says project lead researcher Andrew Stewart, a student at Emory University, US.
“Second, we assume the transmission wavelength of this beam to be one that we can detect. Lastly, we assume that this beacon has been left on long enough for the light to be detected by us. If these requirements are met and the extra-terrestrial intelligence’s beam power and diameter are consistent with an Earth-type civilisation class, our system will detect this signal.”
Hence, the Andromeda photos.
The images being collected by the Las Cumbres Observatory will each capture about one-thirtieth of the galaxy. These will eventually be stitched together to form a single panorama, which will then be compared against another image of the same vista – but this one taken by another facility reflecting pristine conditions free of interfering signals from spacecraft and satellites.
Using the second image as a control and correcting for known sources of interference, Lubin, Stewart and the team will then adjust the Las Cumbres photographs. The result should be two images with identical optical values. If there is a difference, no matter how small, it may indicate an extra-terrestrial signal.
Such a detection, if confirmed, would of course be sensational news – but not necessarily confirmation that humans are not the only technologically competent species in the universe.
Given how far away Andromeda lies, explains project member Jatila van der Veen, a light signal detected from Earth would have been travelling for 2.5 million years – more than enough time for its originating species to have died out.
“That does not mean we should not look,” she says.
“After all, we look for archaeological relics and fossils, which tell us about the history of Earth. Finding ancient signals will definitely give us information about the history of evolution of life in the cosmos, and that would be amazing.”