Fishermen who know exactly what they’re looking for generally use a single line with a specific bait to lure the fish they want. Fishermen who don’t know what they’re looking will often conduct a wide sonar scan hoping to identify any and all kinds of fish and where they’re hiding so they can then assess where to cast their single lines for the best results. The Search for Extraterrestrial Intelligence is like fishing, and those searching are still in the sonar stage. Will they ever move on to single ET lines? A new study gives the answer as of today.
“This is the first technosignature search at a frequency of 155 MHz toward the Galactic Centre (our previous central frequencies have been lower). A blind search toward in excess of 3 million stars toward the Galactic Centre and Galactic bulge is also completed, placing an equivalent isotropic power limit <1.1X10^19W at the distance to the Galactic Centre.”
In this case, the lake is the Milky Way and the fisherman is Chenoa D. Tremblay of the Australian National Association of Scientific and Applied Research. Tremblay’s SETI fish sonar is the Murchison Widefield Array (MWA) of 4,096 dish radio antennas in Western Australia. Being good SETI fishermen, Tremblay’s team focused their search on a spot with a high concentration of areas for hiding ETs – the center of the Milky Way where 144 systems with exoplanets have been identified. However, in case they found nothing there, they also did a blind scan of over three million stars starting in the galactic center and spreading to the galactic bulge around it.
What they were looking for was not physical fishy shadows of ETs but technosignatures – signs of the use of technology by a civilization, in this case low frequency radio waves at 155 MHz. To make sure they weren’t scanning on some galactic center holiday when no ETs were working, the scan took place over seven hours spanning two days.
And the results? (Drum roll, please.)
"No plausible technosignatures are detected."
That’s it. Stop fishing, stop cutting bait, raise the anchor and head for shore … there’s no fish in the best spots and we’re the only fish in the Milky Way.
"However, before we get to all-sky technosignature searches there are a number of computational challenges to overcome and these surveys have provided insight on how to accomplish this goal with an aperture array."
The study authors aren’t quite so pessimistic. While an all-sky scan would be more definitive, no-fish-found scans like this one are helping to refine the search – eliminating radio frequencies and pointing the way towards better ones.
If it was easy, we would have found them already. Or they would have found us.