15Nov2018

Megawatt Earth Lasers Could Attract Alien Astronomers

new study, published in the Astrophysical Journal, suggests that if a 1- to 2-megawatt (MW) laser were focused through a 30- to 45-m telescope and aimed out into space it could reach ET.

James Clark and Dr. Kerri Cahoy propose that laser technology on Earth could emit a beacon strong enough to attract attention of alien astronomers from as far as 20,000 light-years away. Image credit: A. Fitzsimmons, ESO / Sci-News.com.

The combination would produce a beam of infrared radiation strong enough to stand out from the Sun’s energy and attract attention from as far as 20,000 light-years away. Such a signal could be detectable by extraterrestrial astronomers performing a cursory survey of our section of our Milky Way Galaxy — especially if those astronomers live in nearby planetary systems, such as around Proxima Centauri and TRAPPIST-1.

“If we were to successfully close a handshake and start to communicate, we could flash a message, at a data rate of about a few hundred bits per second, which would get there in just a few years,” said lead author James Clark, a graduate student in the Department of Aeronautics and Astronautics at the Massachusetts Institute of Technology (MIT).

“The notion of such an alien-attracting beacon may seem far-fetched, but the feat can be realized with a combination of technologies that exist now and that could be developed in the near term (MW-class lasers, telescopes tens of meters in size).”

Clark and MIT’s Dr. Kerri Cahoy analyzed combinations of lasers and telescopes of various wattage and size, and found that a 2-MW laser, pointed through a 30-m telescope, could produce a signal strong enough to be easily detectable by alien astronomers on Proxima b, a Earth-mass exoplanet that orbits our closest star, 4.23 light-years away.

Similarly, a 1-MW laser, directed through a 45-m telescope, would generate a clear signal in any survey conducted by astronomers within the TRAPPIST-1 planetary system, a system of seven temperate terrestrial planets located 38.8 light-years from Earth.

Either setup could produce a generally detectable signal from up to 20,000 light-years away.

Both scenarios would require laser and telescope technology that has either already been developed, or is within practical reach.

For instance, the researchers calculated that the required laser power of 1 to 2 MW is equivalent to that of the U.S. Air Force’s Airborne Laser, a now-defunct MW laser that was meant to fly aboard a military jet for the purpose of shooting ballistic missiles out of the sky.

They also found that while a 30-m telescope considerably dwarfs any existing observatory on Earth today, there are plans to build such massive telescopes in the near future, including the 24-m Giant Magellan Telescope and the 39-m European Extremely Large Telescope, both of which are currently under construction in Chile.

“Like these massive observatories, a laser beacon should be built atop a mountain, to minimize the amount of atmosphere the laser would have to penetrate before beaming out into space,” Clark said.

Having established that a planetary beacon is technically feasible, the team then flipped the problem and looked at whether today’s imaging techniques would be able to detect such an infrared beacon if it were produced by astronomers elsewhere in our Galaxy.

They found that, while a 1-m or larger telescope would be capable of spotting such a beacon, it would have to point in the signal’s exact direction to see it.

“It is vanishingly unlikely that a telescope survey would actually observe an extraterrestrial laser, unless we restrict our survey to the very nearest stars,” Clark noted.

“We hope the study will encourage the development of infrared imaging techniques, not only to spot any laser beacons that might be produced by alien astronomers, but also to identify gases in a distant planet’s atmosphere that might be indications of life.”

“With current survey methods and instruments, it is unlikely that we would actually be lucky enough to image a beacon flash, assuming that extraterrestrials exist and are making them,” he said.

“However, as the infrared spectra of exoplanets are studied for traces of gases that indicate the viability of life, and as full-sky surveys attain greater coverage and become more rapid, we can be more certain that, if E.T. is phoning, we will detect it.” Source: SciNews

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