The mega-watt laser would have to be built on top of a very high mountain to shorten the distance of atmosphere it passes through, experts have said.
Once in space, the beam could potentially travel up to 20,000 light years away.
James Clark, of the Michigan institute of Technology (MIT), said: ”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.”
His research suggests a 1-to-2-megawatt laser focused through a massive 30-to-45-metre telescope would do the trick.
“This would be a challenging project but not an impossible one”
Even with the sun at close quarters, the beam would stand-out enough for aliens to be interested, the study suggests.
Alien astronomers checking out our section of the Milky Way could potentially live in nearby systems.
Likely suspects are around Proxima Centauri — the nearest star to Earth — or TRAPPIST-1, a star 40 light-years away hosting seven exoplanets, three of which might support life.
These systems are close enough to send a “Morse code” style message in pulses.
“This would be a challenging project but not an impossible one,” the astrophysicist added.
“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.
“I don’t know if intelligent creatures around the sun would be their first guess, but it would certainly attract further attention.”
Although there are no 30 metre telescopes around today, two giants are being built in Chile.
These are the 24 metre Giant Magellan Telescope and the 39 metre European Extremely Large Telescope.
The beam could potentially damage people’s vision if they were to look directly at it, so the study suggests building it on the far side of the moon.
The MIT graduate added: ”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.
“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.
“Optical Detection of Lasers with Near-term Technology at Interstellar Distances” was authored by James R. Clark and Kerri Cahoy and published in The Astrophysical Journal.”