Astronomers from Trinity College Dublin, the Breakthrough Listen project and Onsala Space Observatory have demonstrated the effectiveness of using multisite simultaneous observations for rejecting anthropogenic signals in the search for technosignatures from extraterrestrial intelligences.
The I-LOFAR radio telescope. Image credit: I-LOFAR.
In the last five decades, evidence has steadily mounted that the constituents and conditions necessary for life are common in the Universe.
Predicting specific properties of electromagnetic emissions from extraterrestrial technologies is one of the most challenging aspects of searching for life in the Universe. However, it also represents a high-risk, high-reward endeavor.
If an extraterrestrial civilization were intentionally attempting to indicate its presence through such emissions, it would be advantageous to make the signals easily distinguishable from natural phenomena.
The evidence of such emissions is referred to as technosignatures, and the field dedicated to their detection is known as the Search for Extraterrestrial Intelligence (SETI).
It is commonly assumed that civilizations elsewhere in the Universe may employ similar technologies to those developed on Earth.
Consequently, radio frequencies are considered a logical domain for conducting SETI surveys, due to the widespread use of telecommunications and radar.
Therefore, radio astronomy has played a significant role in the field of SETI since the 1960s.
Numerous previous SETI surveys have utilized large single-dish telescopes operating at frequencies over 1 GHz. However, exploration of the radio window below 1 GHz has been relatively limited.
Technosignature searches commonly seek narrowband (approximately Hz-scale) radio emissions, either transmitted directly or leaking from other civilizations. Nonetheless, there is no inherent preference for any specific segment of the radio spectrum, which necessitates surveys spanning from low frequencies (30 MHz) to high frequencies (100 GHz).
“In the last 50 years evidence has steadily mounted that the constituents and conditions necessary for life are relatively common in the Universe, which begs one of life’s greatest unanswered questions: are we really alone?” said Professor Evan Keane, an astronomer at Trinity College Dublin and the University of Galway, and head of the Irish LOFAR Telescope.
“To some people SETI might seem like something from a movie, but it has been a scientific pursuit for decades, and for a host of very good reasons.”
“With this project we are basing our search on the common assumption that civilisations 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 and our access to next-gen radio telescopes offers a great chance for a deep dive into the Universe.”
In their new study, Professor Keane and colleagues focused on low-frequency SETI in the 110-190 MHz range.
Using the Irish and Swedish LOFAR stations, they scanned 1.6 million star systems flagged as interesting targets by the Gaia and TESS space missions. So far these searches have drawn a blank.
“What makes surveys like this one truly captivating is the fact that we’re pushing these telescopes to their absolute limits, directing them towards substantial portions of the sky,” said Owen Johnson, a Ph.D. candidate at Trinity College Dublin.
“As a result, we have the exciting possibility of discovering all sorts of wild and wondrous phenomena during this process and if we’re very fortunate, even encountering our 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.”
“We have 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.”
The results are published in the Astronomical Journal.
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Owen A. Johnson et al. 2023. A Simultaneous Dual-site Technosignature Search Using International LOFAR Stations. AJ 166, 193; doi: 10.3847/1538-3881/acf9f5
