Sometimes a paper crosses my screen that is science at its most delightful. Today, I get to present one of those papers. In a paper accepted into The Astronomical Journal, a team of graduate students from Penn State University describes how it just might be possible to eavesdrop on alien communications.

Like so many, this team finds the secret sauce for their science in relativity. Any large enough mass has the ability to bend light with its gravity, and our Sun is a large enough mass. In theory, it should be possible to use our Sun’s gravity like a cheap magnifying glass to focus light – including communications signals – onto a relay spacecraft that can beam those signals back to our planet Earth.

This technology was worked out as part of a graduate course at Penn State taught by Jason Wright. In addition to pointing out how this technique can be used to eavesdrop on distant communications, this team also discusses how it can purposely be used to allow humans to communicate across great distances one day. As Wright explains: Astronomers have considered taking advantage of gravitational lensing as a way to essentially build a giant telescope to look at planets around other stars. It has also been considered as a way that humans might communicate with our own probes if we ever sent them to another star. If an extraterrestrial technological species were to use our sun as a lens for interstellar communication efforts, we should be able to detect those communications if we look in the right place. 

We can even imagine a future where star systems with compact objects are one day used as hubs that gather information from one direction and send them off in another. Student Nick Tusay explains: Humans use networks to communicate across the world all the time. When you use a cell phone, the electromagnetic waves are transmitted to the nearest cellular tower, which connects to the next tower, and so on. TV, radio, and internet signals also take advantage of network communication systems, which have many advantages over point-to-point communications. On an interstellar scale, it makes sense to use stars as lenses, and we can infer where probes would need to be located in order to use them.

This is very much future tech that is beyond what we can do today, but solidly in the category of things sci-fi writers should most definitely be including in their stories. To focus a source into an Einstein ring, a space probe would need to be placed 550 AU from the Sun. The Voyager missions are about 160 and 130 AU from the Sun. Right now, we just don’t have propulsion systems or spacecraft power systems capable of getting a relay mission out where it needs to go in a reasonable amount of time or to power it enough to beam high bandwidth data back to us. 

It’s still cool though, and I delight at the chance to eventually read a book where the first researchers use this kind of tech to capture some truly alien entertainment.

More Information

Could we eavesdrop on communications that pass through our solar system? (Phys.org)

“A Search for Radio Technosignatures at the Solar Gravitational Lens Targeting Alpha Centauri,” Nick Tusay et al., to be published in The Astronomical Journal (preprint)