SETI Gets a Boost: Telescopes Working Together to Eliminate False Positives

In the quest to find signs of intelligent life beyond our planet, the Search for Extraterrestrial Intelligence (SETI) has taken a significant step forward by employing simultaneous observations from multiple telescopes to eliminate interference and enhance the search for extraterrestrial radio signals. The new approach, as detailed in a recent study published in The Astronomical Journal, paves the way for more effective technosignature searches and could potentially lead to groundbreaking discoveries.

The history of SETI dates back to 1960, when Dr. Frank Drake conducted the pioneering Project Ozma, using the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. While the initial experiment did not yield any radio signals from space, it laid the foundation for future SETI efforts. Over the years, the search for possible technosignatures has primarily focused on the radio spectrum, but it has been marred by radio interference from Earth-based sources and satellites in orbit, which can result in false positives.

To overcome this challenge, an international team of astronomers, led by Owen A. Johnson from Trinity College Dublin, conducted simultaneous observations from multiple sites. The team included researchers from Breakthrough Listen, the SETI Institute, the Max Planck Institute for Radio Astronomy, the European Southern Observatory (ESO), the Mullard Space Science Laboratory (MSSL), and various universities in Ireland, Sweden, and France. Dr. Simon Pete Worden, the former director of NASA's Ames Research Center and the present Chairman of the Breakthrough Prize Foundation, Breakthrough Initiatives, also contributed to the research.

The most ambitious and comprehensive SETI survey to date is Breakthrough Listen, launched in 2016. This ten-year initiative aims to examine over one million stars closest to Earth, the center of our galaxy, the entire galactic plane, and the 100 closest galaxies to our own. It focuses on radio technosignatures while also keeping an eye out for optical laser transmissions.

Traditionally, SETI experiments were constrained by sensitivity and scope, limiting searches to the Ultra-High Frequency (UHF) and low-microwave range. However, advancements in technology have significantly improved the sensitivity of astronomical instruments, enabling broader sky coverage. This progress allows researchers to explore more of the radio band, including the previously unexplored low-frequency radio range.

The key innovation in the recent study was the use of two identical telescopes at distant locations (Ireland and Sweden) to cross-reference detected signals. This approach effectively eliminated false positives arising from terrestrial sources and interference, enhancing the precision of their observations.

The team conducted simultaneous observations of 1,631,198 targets identified by NASA's Transiting Exoplanet Survey Satellite (TESS) and the ESA's Gaia Observatory in the Milky Way, in the 110–190 MHz range using the Netherlands Institute for Radio Astronomy (ASTRON) Low-Frequency Array (LOFAR) stations. The results were encouraging, ruling out the presence of Doppler-drifting narrowband signals from hundreds of thousands of stellar systems in our local galaxy, without any false positives.

While the study did not discover evidence of transmission technologies from the surveyed stars at the specified frequencies, it demonstrated that simultaneous observations are an effective way to eliminate uncertainty in SETI searches. This finding opens up the possibility of exploring the previously uncharted low-frequency radio spectrum without interference, potentially leading to more robust SETI surveys in the future.

Looking ahead, Owen A. Johnson plans to conduct a Low-Frequency Pulsar, Fast Radio Burst (FRB), and Technosignature search with LOFAR in the coming year, with the aim of refining the technosignature parameter space at this frequency and potentially making exciting discoveries of exotic transients. As the search for extraterrestrial intelligence continues to evolve, the future of SETI research appears brighter than ever, with telescopes double-checking each other to enhance our chances of discovering signs of intelligent life beyond Earth.