According to new research, a strange radio signal previously believed to be a possible sign of extraterrestrial intelligence in the Proxima Centauri system was actually of terrestrial origin.
A few months ago, a team of astronomers announced the detection of a strange radio signal in the direction of Proxima Centauri, the stellar system closest to the sun (about 4.2 light-years), thanks to the Parkes radio telescope, in Australia. During a 26-hour survey, specifically, the telescope recorded more than four million radio signals from the system's surroundings, but one radio burst, recorded over about five hours, seemed to stand out both for its long duration and its particular wavelength.
Indeed, the astronomers had recorded a "narrowband" signal, meaning that it occupied only a narrow range of radio frequencies (982 MHz) . However, to our knowledge, only our satellites are capable of compressing electromagnetic energy in a single frequency bin like this. However, the team quickly ruled this out.
On the other hand, we also know that this system hosts a possibly habitable Earth-sized rocky planet (Proximal b). Finally, the signal, dubbed Breakthrough Listen Candidate 1 (or BLC-1), appeared to have "evolved" slightly during its five-hour observation, suggesting that it originated from a moving planet.
The discovery had tickled the curiosity of SETI scientists. Unfortunately, this signal had only been detected once, in the spring of 2019, effectively preventing a real follow-up study. Skeptics then argued that it could possibly be a new form of radio interference generated by our earthly activities . And they were right.
Actually, it was "man-made radio interference from technology, probably on the surface of the Earth “, emphasizes Sofia Sheikh, of the University of California at Berkeley and co-author of two new studies published in Nature Astronomy.
As part of this work, since the signal did not reappear in subsequent observations of the star, the researchers took a closer look at their initial data. They then discovered that their automated sorting program had previously ignored several signals very similar to BLC1, but emitted at different frequencies.
The researchers ultimately concluded that BLC1 and these "look-alike" signals were components of the same radio source . Also, this radio source probably came from Earth , somewhere a few hundred kilometers from the Parkes Murriyang Telescope. For the team, the fact that BLC1 only appeared during this five-hour observation of Proxima Centauri is probably just a coincidence.
Since the signal never reappeared, it is possible that it came from faulty electronic equipment . The frequency range in the signal was also "consistent with common clock oscillator frequencies used in digital electronics “, wrote the researchers, suggesting that a nearby phone or computer could have produced this famous “alien signal”. They plan further studies to determine precisely this source.
