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An MIT study suggests that laser technology on Earth could emit a beacon powerful enough to attract attention as far away as 20,000 light-years away. Credit: MIT News
If extraterrestrial intelligence exists somewhere in our galaxy, a new MIT study suggests that laser technology on Earth could, in principle, be transformed into a kind of planetary porch light – a beacon powerful enough to draw attention to a distance as far as 20 000 light-years.
The research, which author James Clark calls a "feasibility study", appears today in the Astrophysical Journal. The results suggest that if a powerful 1 to 2 megawatt laser was focused in a giant 30 to 45 meter telescope and directed in space, the combination would produce a beam of infrared radiation strong enough to stand out from the rest of the world. ;screen. the energy of the sun.
Such a signal could be detected by extraterrestrial astronomers performing a rapid survey of our section of the Milky Way, especially if these astronomers live in nearby systems, such as Proxima Centauri, the closest star to the Earth, or TRAPPIST -1, a 40 light-years away, it houses seven exoplanets, three of which are potentially habitable. According to the study, if the signal is detected by any of these close systems, the same megawatt laser could be used to send a brief message in the form of similar impulses to the Morse code.
"If we managed to close a handshake and start communicating, we could send a message, at a data rate of a few hundred bits per second, that would arrive in a few years," says Clark, a graduate student. in the Department of Aeronautics and Astronautics at MIT and author of the study.
The notion of such a lighthouse attracting extraterrestrials may seem far-fetched, but Clark says that the feat can be achieved with a combination of existing technologies and can be developed in the short term.
"It would be an ambitious project but not impossible," said Clark. "The types of lasers and telescopes built today can produce a detectable signal, so that an astronomer can take a look at our star and see something unusual immediately." I do not know if intelligent creatures around the sun could be their first hypothesis, but it certainly would attract more attention. "
Standing in the sun
Clark began studying the possibility of a planetary beacon as part of the final project of 16.343 (Aircraft and Aircraft Sensors and Instrumentation), a course taught by Associate Professor Kerri Cahoy, a consultant. from Clark.
"I wanted to see if I could take the types of telescopes and lasers we are building today and make them a detectable beacon," says Clark.
It started with a simple concept including a large infrared laser and a telescope to further focus the intensity of the laser. Its goal was to produce an infrared signal at least 10 times higher than the natural variation of infrared emissions from the sun. Such an intense signal, it was enough, would be enough to distinguish itself from the infrared signal of the sun, in any "summary investigation carried out by an extraterrestrial intelligence".
He analyzed combinations of lasers and telescopes of different powers and sizes, and discovered that a 2-megawatt laser directed at a 30-meter telescope could produce a signal powerful enough to be easily detectable by astronomers from Proxima Centauri b, a planet revolves around our nearest star, 4 light years away from us. Similarly, a 1-megawatt laser led by a 45-meter telescope would generate a clear signal in any survey conducted by astronomers within the TRAPPIST-1 planetary system, about 40 light-years away. Either configuration, he said, could produce a generally detectable signal at a distance of up to 20,000 light-years.
Both scenarios would require laser and telescope technology already developed or within reach. For example, Clark calculated that the required laser power of 1 to 2 megawatts was equivalent to that of the Airborne Laser of the US Air Force, a now-defunct megawatt laser that was to fly on board a military aircraft in the purpose of launching ballistic missiles. from the sky. He also found that, while a 30-meter telescope far surpasses any existing observatory on Earth, it is planned to build such telescopes in the near future, including the 24-meter Giant Magellan telescope and the 39-meter European Extremely Large telescope. meters, which are currently under construction in Chile.
Clark envisions that, like these massive observatories, a laser beacon should be built on top of a mountain, in order to minimize the amount of atmosphere that the laser should penetrate before radiating into the sky. # 39; space.
He acknowledges that a megawatt laser would come with security issues. Such a beam would produce a flux density of about 800 watts of power per square meter, which is close to that of the sun, which generates about 1,300 watts per square meter. Although the beam is not visible, it could still hurt people's vision if he looked at it directly. The beam could also scramble all the cameras on board a spacecraft.
"If you wanted to build this thing on the other side of the moon, where no one would live or be in orbit, then it could be a safer place," says Clark. "In general, it was a feasibility study.It's a good idea or not, it's a question of discussion for future work. "
Take the call of E.T.
After establishing the technical feasibility of a planetary beacon, Clark reversed the problem and investigated whether current imaging techniques would be able to detect such an infrared beacon if it was produced by astronomers elsewhere in the galaxy. He found that even if a telescope of one meter or more would be able to spot such a beacon, it should indicate the exact direction of the signal to see it.
"It is highly unlikely that a telescope survey is observing an alien laser unless we limit our survey to the nearest stars," Clark says.
He hopes the study will encourage the development of infrared imaging techniques, not only to identify laser beacons that can be produced by extraterrestrial astronomers, but also to identify gases in the atmosphere of a distant planet that could indicate life.
"With the current methods and instruments of investigation, it is unlikely that we will have the chance to image a beacon flash, assuming that aliens exist and are making them," Clark says. . "However, as the infrared spectra of exoplanets are studied for traces of gas indicating the viability of life, and the open-air surveys reach greater coverage and become faster, we can be more certain that, if AND call, we will detect it. "
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More information:
Optical detection of lasers with short-term technology at interstellar distances, Astrophysical Journal (2018). DOI: 10.3847 / 1538-4357 / aae380
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