SETI Could Hunt Alien Transmitters in the Solar System

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We now have the technology to go snooping for extraterrestrials in our own backyard. No, not as close as little green men cutting up crop circles; instead, we should be able to detect an alien device positioned somewhere between the sun to 30 times farther out than Pluto.

What would aliens place 100 billion miles from the sun? Michael Gillon of the Observatory of Geneva, Switzerland wrote in a recent paper that extraterrestrials who are surveying our solar system with one or more artificially intelligent probes would need to set up a very powerful transmitter to the send data back to their home planet.

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Green-minded (not necessarily green-skinned) aliens could save a lot of power and sidestep complex engineering by simply using the sun’s gravitational field as a powerful amplifier for sending and receiving messages from the home star. This phenomenon, called gravitational lensing, amplifies electromagnetic radiation just as a magnifying glass brightens the light from a source (as depicted in the artist’s impression above).

The home civilization would need a similar receiver set up at star’s so-called solar focal point. The transmitter/receiver pair would have their signals turbo boost by a factor of 500 billion billion times by gravitational lensing.

In fact, space scientist Claudio Maccone of the International Academy of Astronautics has argued that by solely using the gravitational focusing potential of the sun that we would be able to communicate with a probe sent to any of the nearest stars. So much for an abandoned alien “phoning home” with  a transmitter fashioned from an umbrella and household batteries in the 1982 film, “E.T. The Extra-Terrestrial.”

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The alien transmitting antenna could weigh as little as one ton and have a radio dish no bigger than one of the “orchard” of 82-foot diameter antennas at the Very Large Array radio telescope facility near Socorro, New Mexico.  This means it would be too small to photograph or detect if it passed in front of a star.  A powerful enough interplanetary LIDAR or radar, located aboard an interstellar probe set to intercept a preselected solar focal region for a given star, could look for the artifact.

But where to look on the celestial sphere? For starters, point a telescope to a location on the celestial sphere 180 degrees from Alpha Centauri. This is the place Centauri astronomers would need to locate a relay station.

The Allen Telescope Array in Northern California could look for anomalous radiation at a solar focal region that aligns with out sun and Alpha Centauri (shown here at visible, infrared and radio wavelengths). This neighboring star system could potentially harbor advanced life. If unusual “leakoff” signals were found, a probe could be launched on a very long mission to check out the region.

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The SETI effort would next monitor the solar focal regions of the most nearest stars, scouted out by NASA’s upcoming TESS mission,  to search for alien transmitters.

Gullion points out that our solar system has a staggering volume of 500 trillion cubic astronomical units out to the Oort Cloud (1 AU is the average Earth-sun distance), so the solar system remains virtually unexplored for any alien artifacts. This means there is plenty of elbowroom for E.T. to go hide a clandestine transmitter.

Image credit: NASA, M. Gullion