A team of astrophysicists from Trinity College Dublin and Onsala Space Observatory in Sweden are searching for extraterrestrial radio signals in the hopes of finding signs of intelligent alien life. The team is using both the Irish LOFAR telescope and its counterpart in Onsala, Sweden to monitor millions of star systems. Professor Evan Keane, Associate Professor of Radio Astronomy in Trinity’s School of Physics and Head of the Irish LOFAR Telescope, plans to monitor millions of star systems. The research is being supported by Science Foundation Ireland and will rely on machine learning techniques to sift through the immense volume of data.

For over 60 years, scientists have been searching for extraterrestrial radio signals, many of which have been conducted using single observatories. Unfortunately, this method has limited the ability to identify signals from the haze of terrestrial interference on Earth. Most of the effort has focused on frequencies above 1 GHz, as the single-dish telescopes employed operate at these frequencies.

Now, a new collaboration led by Trinity College Dublin, with the Breakthrough Listen team and Onsala Space Observatory in Sweden, is perfecting a multi-site, multi-telescope technique that allows them to search at much lower frequencies of 110 – 190 MHz.

The Breakthrough Listen program is a comprehensive search for technologically advanced extraterrestrial life. The program is developed with dedicated instruments at the Irish and Swedish LOFAR stations. One of the significant benefits of using multiple sites is that it reduces the likelihood of a "false positive" signal. Such signals can arise due to interference from various human sources on Earth.

The team has recently published details of their method and their ongoing search in the Astronomical Journal. They have already scanned 1.6 million star systems flagged as interesting targets by the Gaia and TESS space missions, run by ESA and NASA, respectively. So far, these searches have not yielded any results, but the search has only just begun.

Prof. Keane commented that evidence has steadily mounted over the last 50 years that the constituents and conditions necessary for life are relatively common in the Universe. This begs one of life's greatest unanswered questions: are we alone? The search for extra-terrestrial intelligence, or SETI, may seem like something from a movie to some people, but it has been a scientific pursuit for decades and a host of very good reasons.

With this project, the team is basing their search on the common assumption that civilizations elsewhere in the Universe may employ similar technologies to those developed on Earth. As a result, radio frequencies are a logical domain for conducting SETI surveys due to the widespread use of telecommunications and radar. The team's access to next-generation radio telescopes offers a great chance for a deep dive into the Universe.

Owen Johnson, PhD Candidate in Trinity's School of Physics, is the first author of the journal article, and the first Irish person to ever undertake a PhD on the topic of SETI. He added that what makes surveys like this one truly captivating is the fact that they are pushing these telescopes to their absolute limits, directing them toward substantial portions of the sky. As a result, they have the exciting possibility of discovering all sorts of wild and wondrous phenomena during this process and if they are very fortunate, even encountering cosmic neighbors.

LOFAR is soon to undergo a staged series of upgrades across all stations in the array across Europe, which will allow an even broader SETI at ranges of 15 - 240 MHz. The team has billions of star systems to explore and will be relying on some machine-learning techniques to sift through the immense volume of data.

"That in itself is interesting – it would be fairly ironic if humankind discovered alien life by using artificial intelligence," Owen Johnson concluded.