Radio Signals from Proxima Centauri


By Allison Kubo Hutchison

Parke Radio Telescope detected unnatural signals from the region around Proxima Centauri on April 29 2019. Photo by Stephen West.

Scientists at the Search for Extraterrestrial Intelligence (SETI) have detected a narrow band of radio signals coming from a narrow area around Proxima Centauri, our nearest neighbor star at 4.2465 light-years away. Observed on April 29, 2019, the signal dubbed Breakthrough Listening Candidate 1 (BLC1) was detected at a frequency of 982.002 MHz with little scatter which makes it a candidate for a technosignature, a sign of intelligent life. Radio signals are naturally produced by various stellar and planetary bodies due including our sun and Jupiter however these occur over a broadband of frequencies. The needle-like thin signal is difficult to explain by natural processes.

Of course, the signal could be from intelligent life; it could be our own signal. Humans produce huge amounts of radiation from WiFi, cellphones, satellites, and microwave lunches. A human-made signal from a satellite in the same vicinity of the sky as Proxima Centauri could have produced the tone. However, it was observed using the Parkes radio telescope in Australia which is far south from the ecliptic where the majority of the satellite orbit. Fast Radio bursts at the Parkes radio telescopes have stumped us in the past until it was revealed to originate from microwave ovens in the break room.

The signal does have a drift in it which is still to be interpreted. One possibility is that the drift in the signal might be due to a change in the location of the transmitter as if it were an orbiting planet. Due to the doppler effect, when the observer or transmitter of a wave changes velocity the frequency will change according to their acceleration. On Earth of course we are always moving in orbit around the sun which will impart a specific negative drift to the signal. However, the effect seen is the opposite implying that the location of the signal is also accelerating.

However, a recent paper released in The Astrophysics Journal documented the April 2019 radio bursts linked to stellar flare from the brown dwarf Proxima Centauri. These flares due to instabilities in the star’s strong magnetosphere emit ionizing radiation and longwave radiation and could be a source of the signal but would not fully explain its narrow band. Additionally, these bursts from the star call habitability into question because any planet near the star would be subject to large amounts of ionizing radiation.

This signal was only detected once so far by astronomers at the Breakthrough Listen project. In order for it to be a technosignature the signal has to pass a series of intensive checks by SETI. The narrow band is one, however, it also needs to be repeated. This signal is one of two which have been thought to be alien in origin but have not been repeatedly observed. The Wow! Signal received at the Ohio State University’s Big Ear radio telescope in 1977 was another narrow band detached at 1420.4556±0.005 MHz.

Jerry R. Ehman’s notes on the 1977 signal. Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO).

The search for the culprit whether it be man, beast, or microwavable burrito continues. You can be a part of it too through the SETI@home initiative which lends your computer’s processor power to decoding more radio telescope data in search of intelligent life. It is still unclear what the explanation is for BLC1 and for the Wow! Signal. We have to keep our eyes and ears open and face out toward the dark.

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