- A feasibility study proposes that the laser and telescope technology on earth could be used as a beacon to attract the attention of aliens.
- One needs to direct 1- to 2-megawatt laser through a 30- to 45-meter telescope into space.
- The same laser could be sent with a brief message encoded in 5×5 tap code or Morse code.
Could we use existing telescope and laser technology to signal a nearby extraterrestrial intelligence (if there is any)? Could we develop a strong enough laser beam and direct it towards nearby exoplanets? How fast the data could be sent once contact is made?
These questions are answered by two researchers, James Clark and Kerri Cahoy, in a study published in the Astrophysical Journal. According to them, the laser technology on Earth could be used as a beacon to attract the attention of aliens from a distance of up to 20,000 light years.
To do this, one needs to focus a powerful laser (from 1 to 2 megawatt) through a large telescope (30 to 45 meter wide) and aim out into space. The infrared radiation beam generated by this combination would be stronger than the Sun’s energy.
Brief Message Encoded Into Laser
An alien astronomer (considering there is one) could perform a cursory survey of our region in the Milky Way to detect such signals. It would be easier to detect these signals from nearby systems like Proxima Centauri and TRAPPIST-1 star.
If either of these stars detects the signal, the same laser could be sent with a brief message encoded in the form of pulses similar to 5×5 tap code or Morse code. To close a handshake and initiate communication, a message could be flashed at several hundred bits per second, which would take just a few years to get there.
The concept seems far-fetched, but according to the researchers, we can achieve this feat with technologies that exist today and that could be developed in the coming years.
To look into possibilities, they focused on the laser’s intensity. They examined combinations of telescopes and lasers of various size and wattage, and discovered that if a 2-megawatt laser is directed through a telescope as large as 30 meters, it could generate a signal powerful enough to be detected from Proxima Centauri b, an exoplanet (about 4 light-years away) orbiting the closest star to the Sun.
In the same way, if 1-megawatt laser is pointed through a 45-meter telescope, it would produce a signal that could be detected within the ultracool red dwarf star, TRAPPIST-1, nearly 40 light-years away. Both setups can create a predominantly detectable signal from as far as 20,000 light years away.
The 2-megawatt laser is equivalent to that of the United States Air Force’s Boeing YAL-1 Airborne Laser, a missile defense system developed to destroy tactical ballistic missiles. Although the current largest optical telescope is only 10.4 meters long (in diameter), there are plans to construct giant telescopes within the next decade, including 39-meter ESO’s Extremely Large Telescope and 25-meter Giant Magellan Telescope.
Moreover, if such signals were generated by aliens elsewhere in the galaxy, a telescope larger than one meter would be able to spot such a beacon. However, to observe it, the telescope would have to focus in the exact direction of the signal.
It wouldn’t be safe to build such a powerful beam here on Earth: it would generate approximately 800 watts per square meter of flux density, which could destroy human vision and scramble instruments aboard satellites that happen to pass through it. According to the researchers, a better place for this thing would be the far side of the Earth’s Moon.
This is just a feasibility study: whether to implement this or not is a subject of future discussion.