Astronomers from the Breakthrough Listen project conducted a targeted search for artificial radio signals in the system of LHS 1140. The focus was on the exoplanet LHS 1140 b, which was recently found to have a tenuous helium atmosphere — making it one of the most promising «super-Earths» for astrobiology. Using archival data from the 100-meter Green Bank Telescope (GBT), scientists scanned frequencies from 1 to 12 GHz, looking for signals that couldn’t be explained by natural processes.
After filtering out terrestrial and other natural interferences, no technological markers were detected. However, the absence of signals was still a valuable result: the researchers calculated the minimum effective isotropically radiated power (EIRP) that their system could have detected. They set a threshold of 300 gigawatts — meaning that if there were a continuous narrowband radio transmitter in the system, its energy would not exceed this value (otherwise it would have been picked up). For context, all of Earth’s cellular communication emits about 3 GW, while the famous Arecibo planetary radar had a power of about 20 TW. The study also notes that signal transmission through stellar wind could broaden and weaken artificial bursts, potentially reducing sensitivity. Further listening to LHS 1140 is planned using the Allen Telescope Array, which should increase sensitivity and expand the frequency range.
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