How can star populations help astronomers re-evaluate the search for intelligent extraterrestrial life, also called technosignatures? This is what a recently submitted study hopes to address as a team of scientists investigated the parameters of identifying locations of technosignatures, also called extraterrestrial transmitters. This study has the potential to help astronomers constrain the criteria for finding intelligent life in both our galaxy and throughout the universe.
For the study, the researchers used a widely used tool called a Besançon Galactic Model (BGM), which is designed to simulate star populations throughout the Milky Way Galaxy, including star type, distribution, distance, physical characteristics, brightness, and motions. The purpose of the model ties into the goal of the paper, which is to identify “hidden” stars that go unseen by traditional surveys like Kepler, Gaia, and Breakthrough Listen but fall into a radio telescope’s field of view, also called stellar “bycatch”. In the end, the researchers successfully expanded the number of stars that SETI can use to search for technosignatures while also eliminating human-based bias that have traditionally contributed to SETI and technosignature searchers.
The study notes in its conclusions, “This paper builds on the approach of Wlodarczyk-Sroka et al. (2020) by emphasising the importance of including the stellar bycatch for targeted radio SETI observations. By simulating stars within the field of view using the BGM, we can overcome the observational limitations of Gaia and improve upon statistical estimates of the prevalence of extraterrestrial transmitters across a broader stellar population, including lines of sight susceptible to confusion and crowding.”
The researchers note how this study could be used to enhance future SETI searches for technosignatures, including the use of a web-based calculator called the SETI-Stellar-Bycatch-Simulator. The calculator uses input from the user, including coordinates and field of view, to simulate where stars throughout the Milky Way and where extraterrestrial transmitters might potentially be located.
To date, the closest humanity has come to identifying a technosignature was the Wow! Signal, which was an event that occurred on August 15, 1977, at the Big Ear Radio Telescope at Ohio State University. While the signal itself was not directly heard, it was later discovered by astronomer Jerry Ehman after sifting through data, and after nothing the sequence of numbers “6EQUJ5”, he wrote the word “Wow!” on the printout. The reason this remains the closest signal to a technosignature is due to eliminating possible sources, including Earth-based interference, satellite transmissions, and natural astrophysical sources.
This study comes as SETI and other organizations worldwide continue scanning the heavens for signs of intelligent life beyond Earth. While technosignatures are often attributed to radio signals, they can also come in the form of optical & infrared lasers, megastructures like Dyson spheres or planetary-scale engineering, atmospheric pollutants, and waste heat.
As noted above, one of the programs searching for technosignatures is the Breakthrough Listen project, which is a SETI project started in 2015 that uses radio telescopes across the globe for searching for technosignatures, including USA, Australia, South Africa, and China. Examples of specific exoplanet systems that Breakthrough Listen targets include TRAPPIST-1, Proxima Centauri, Tau Ceti, 51 Pegasi, Kepler & TESS planet hosts, LHS 1140, and GJ 273 (Luytens Star), the last of which the project sent a reply message for a project.
As humanity continues searching the heavens for signs of intelligent life, SETI and other projects will continue developing new and exciting methods for narrowing the scope regarding where we could search and identify technosignatures.
What new insight into star populations and technosignatures will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!