Astronomers are studying a mysterious radio signal that came from the nearby star Proxima Centauri

Astronomers in the Breakthrough Listen project to search for intelligent life in the universe report a mysterious radio signal coming from Proxima Centauri, the closest star to the solar system . This is the first radio signal that can not be attributed to electromagnetic interference from our civilization or to natural sources – in the meantime.

The narrow electromagnetic signal, called BLC1, was received for 30 hours in April and May last year by the Parks Radio Telescope in Australia. Since then, Breakthrough Listen scientists have been studying the signal, and so far have not found a terrestrial explanation, such as a passing satellite in space or radio broadcasts on Earth.

Contrary to popular belief, which originates in movies like “Contact”, Breakthrough Listen does not listen to the silence of the night sky. In fact, radio signals are constantly being picked up at the Parks Radio Telescope or at the Green Bank Observatory in West Virginia. But every such letter has a natural or human-artificial source. Humanity produces a lot of noise, and in Breakthrough Listen we try to separate our radio broadcasts from radio broadcasts that may be emanating from outer space.

It is likely that the new “broadcast” from Proxima Centauri will also eventually find a simple explanation, but in the meantime it seems that it is nonetheless exceptional in some respects. First, it is very narrow – around 980 MHz – which works with artificial frequency division. And second, the frequency repetition during those 30 hours corresponds to what we would expect from a planet’s motion.

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Proxima Centauri B simulation, a planet in the 3-star Alpha Centauri system. 
To the right of the red dwarf you can see the other 2 stars 
ESO / M. Grain knives

The source of the study, which has not yet been published in an academic journal, told the British Guardian that Breakthrough Listen has not been able to pick up the signal again since May 2019.

Proxima Centauri B – Earth Twin?

Just 4.2 light-years away, Proxima Centauri is the closest cosmic neighbor to the solar system. The star, a red dwarf, is surrounded by at least two planets. The closest of the two planets, Proxima Centauri B , is probably a rocky planet with a mass of 1.17 Earth mass – and is located in the seating area of the Proxima Centauri system , ie at the right distance from the planet to allow liquid water to exist on the surface. The second planet found, Proxima Centauri C, is probably a distant and cold gas giant, similar to Neptune .

Among astronomers, there is a lively debate about the potential for life on extrasolar planets orbiting red dwarfs like Proxima Centauri. Because they are small and relatively cold in the sun, the planets that surround them do so from a remarkably short distance. Proxima Centauri B for example orbits the red dwarf Proxima Centauri from a distance of 7.5 million km. For comparison, the closest hot star to our sun orbits it from a distance of almost 70 million km.

From such a distance, the planets may be gravitationally locked on the planets, similar to the moon on Earth , so that half will always be illuminated and half will always be dark. Moreover, many red dwarfs – and Proxima Centauri is no exception – are flash stars: stars with extremely strong magnetic activity, prone to powerful and frequent solar flares. It is unclear whether life could evolve on a planet located near such an active red dwarf, in part because eruptions could strip a planet of its atmosphere.

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