From The Editors Science

MIT Researchers Say Existing Laser Technology Could Be Tweaked to Attract Alien Astronomers

According to a new study conducted by researchers at the Massachusetts Institute of Technology (MIT), existing laser technology could be tweaked to serve as a “planetary porch light” that could potentially attract the attention of alien astronomers from outer space – if at all they do exist.

The paper, published in the Astrophysical Journal this week (Nov 5), basically talks about the possibility of producing an infrared laser beam powerful enough to penetrate as deep as 20,000 lightyears into space and, of course, detectable enough to be spotted by alien astronomers looking out for such signals.

The paper suggests that focusing a high-powered 1- to 2-megawatt laser through a 30- to 45- meter telescope aimed into space could produce the desired beam.

“Lasers have a unique ability to precisely drive, manipulate, control, and probe matter utilizing an incredible variety of methods,” says an Optical Society of America (OSA) article published on the PHYS.ORG website.

“While they often operate behind the scenes, lasers are the backbone of revolutionary science and technology—including research advances that were the basis for the 2018 Nobel Prize in Physics,” the article states.

The infrared beam would have to outshine the sun for it to be spotted by extra-terrestrial stargazers performing a cursory survey of our neck of the woods in the Milky Way, particularly if they happen to be located in neighboring star systems, such as the Proxima Centauri and the TRAPPIST-1 and their respective exoplanets orbiting them.

Proxima Centauri b is the exoplanet orbiting Proxima Centauri, a mere 4.2 light years away from Earth, and is said to be in what scientists call the “habitable zone” of the red dwarf star.

The habitable zone of a star system is, basically, the ideal distance from the parent star to support life of any kind – not too close to be too hot for liquid water formation, neither too far for water to be in a permanent freeze.

The TRAPPIST-1 system, on the other hand, is more distant at 39 lightyears from Earth, with at least seven exoplanets orbiting the ultra-cool dwarf star, as revealed in a study published in the journal Nature in February 2017.

These exoplanets are temperate and terrestrial, much like our very own Earth and are similar in size as well.

They orbit in close proximity to the parent star, and to each other, forming a relatively tight cluster.

Researchers believe that three of the exoplanets closest to TRAPPIST-1 are too hot to support liquid water, while the farthest will likely be too cold, leaving just the 4th, 5th, and 6th exoplanets in the so-called habitable zone.

In the event the signal is detected by alien astronomers in one of these systems, the same megawatt laser could be deployed to beam a brief Morse code-like message.

“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 James Clark, an MIT undergraduate in the institute’s Department of Aeronautics and Astronautics and lead author of the paper.

“This would be a challenging project but not an impossible one,” he said.

As improbable as the idea may seem, Clark is of the opinion that considering the kind of technologies at our disposal today, it should be a matter of time before we can produce a signal strong enough to catch the attention of our extraterrestrial neighbors.

“The kinds of lasers and telescopes that are being built today can produce a detectable signal, so that an astronomer could take one look at our star and immediately see something unusual about its spectrum,” Clark said.

“I don’t know if intelligent creatures around the sun would be their first guess, but it would certainly attract further attention,” he said.

While Clark seems to be convinced about the technical feasibility of such a planetary beacon, he does acknowledge the fact that a laser as powerful as the one his study proposes could present safety issues.

A 1- to 2-megawatt laser would generate a flux density (the amount of magnetic, electric, or other flux passing through a unit area) of some 800 watts per square meter (the sun produces about 1,300 per sq. meter), capable of impairing the vision of people looking directly at it, even though the beam would be invisible to the naked eye.

Spacecraft passing through the beam would also be vulnerable to equipment malfunction and damage.

“If you wanted to build this thing on the far side of the moon where no one’s living or orbiting much, then that could be a safer place for it,” Clark said.

“In general, this was a feasibility study. Whether or not this is a good idea, that’s a discussion for future work,” he added.

Once Clark had established, at least in theory, that the right kind of infrared beam had the potential to be detected by alien astronomers, he wanted to have a reverse perspective of the scenario.

He wanted to find out if we had the imaging techniques to intercept a similar signal beamed by our Milky Way neighbors, probably with the same purpose in mind as ours.

His study led him to the conclusion that a meter-long telescope could possibly do the job, provided the survey was restricted to nearby stars and the telescope was aimed at the incoming signal’s precise direction.

“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 said.

“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.”

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