Is there life outside Earth? This question turns out to be one of the most difficult in science. Despite the seemingly limitless space of the universe, the great distances between stars suggest abundant potential for life, making the search akin to finding a needle in a cosmic haystack.

The search for extraterrestrial intelligence (SETI) is a branch of astronomy dedicated to the search for extraterrestrial life by searching for unusual signals called technosignatures. The identification of a technosignature would not only mean the existence of life, but would also specifically point to the existence of intelligent life with the help of advanced technologies. However, 60 years of search is still not enough. But now my colleagues and I have begun investigating a previously unexplored frequency range.

SETI suggests that extraterrestrial civilizations could rely on technology in the same way as humans on Earth, such as using cell phones, satellites, or radar.

Since most of this technology produces highly visible signals at radio frequencies, focusing on these wavelengths is a logical starting point in the search for potential extraterrestrial intelligence. Previous technosignature studies only covered the radio frequency range above 600 MHz, leaving lower frequencies largely unexplored. This is despite the fact that everyday communications services such as air traffic control, maritime distress broadcasts and FM radios emit such low-frequency radiation to Earth.

The reason it has not been studied is that telescopes operating at these frequencies are quite new. And lower frequency radio waves have less energy, meaning they are harder to detect.

In our latest research, we ventured into these frequencies for the first time.

The Low Frequency Array (Lofar) is the world’s most sensitive low-frequency telescope operating in the 10-250 MHz range. It consists of 52 radio telescopes scattered across Europe. These telescopes can achieve high resolution when used together.

However, only two stations were used in our study, one of which is located in Birr, Ireland, and the other is located in Onsal, Sweden. We examined 44 planets orbiting stars other than our Sun, detected by NASA’s Transiting Exoplanet Survey Satellite. We scanned these planets for two summers with our two telescopes at frequencies between 110 and 190 MHz.

It doesn’t seem like much of a target at first, but low-frequency surveillance provides a huge advantage due to its wide field of view compared to its high-frequency counterparts. This is because the area covered by the sky decreases with higher frequencies.

In the case of Lofar, we covered 5.27 square degrees of sky for each orientation of our telescopes. This resulted in 36,000 targets per telescope; or if you check what other stars are nearby and include their planets, there are over 1,600,000 targets in total.

Interfering signals

Searching for technosignatures from space poses a significant challenge; The same technosignatures exist everywhere on Earth. This is a hurdle because the telescopes in these searches have sensitivity levels that can detect signals similar to a phone call coming from the other end of the solar system.

As a result, the data collected is filled with thousands of signals coming from Earth, creating significant difficulties in isolating and identifying signals that may be of extraterrestrial origin. Having to sift through this large and noisy data set makes the search difficult.

To reduce such RF interference, we proposed an innovative approach called the “deny-to-pair” method. This takes into account the local radio emission of each of our telescopes. For example, if I use a phone near a telescope in Ireland to call my supervisor, the same call will not show up in data in Sweden and vice versa (due to the telescope not being pointed in our direction, but pointing at an exoplanet). applicant).

As a result, we decided to include signatures in the dataset only if they had a simultaneous presence at both stations; this suggested that they came from extraterrestrial origin.

In this way, we focused on thousands of candidate signals. This means we haven’t found any signs of intelligent life in our search, but we’re just getting started, and there are likely plenty of Earth-like planets out there. Knowing that the method of rejecting luck works with a high success rate could be a key to helping us detect life on one of these planets in the future.

There are many ways to find technosignatures at low frequencies. A sister study (Nenufar) operating at a frequency of 30-85 MHz is currently being conducted. However, Lofar’s follow-up observations will increase the scope of the study tenfold next year. The data collected is also about pulsars, fast radio bursts, radio exoplanets, etc. It is also used to examine astronomical objects known as.

Fortunately, we are just at the beginning of a long journey. I have no doubt that very surprising things will happen. And if we’re lucky, we might get the ultimate prize: a company in space.