Did Earth Receive a Radio Transmission From Proxima Centauri? 

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The Parkes radio telescope in eastern Australia, a 64-meter radio dish operated by the Commonwealth Scientific and Industrial Research Organisation (CSIRO).  (CSIRO)

A team of astronomers is hard at work analyzing an unusual radio signal detected early in 2019 by the Parkes telescope, a 64-meter radio dish in eastern Australia. The signal appears to have come from the direction of Proxima Centauri, the nearest star to our solar system, and its characteristics are more typical of an artificial broadcast than a natural radio source. 

Is this the long-awaited sign of intelligent life out there among the stars, proof that we are not alone in the universe? More exciting — or concerning, depending on how you feel about space aliens — are there ETs living in the next star system over, our closest neighbor in the galaxy? 

It’s tantalizing to imagine this. 

Hubble Space Telescope image of the red dwarf star Proxima Centauri, the smallest and faintest member of the triple Alpha Centauri star system, and the closest star to our solar system. (ESA/NASA/Hubble)

However, even the signal’s discoverers, researchers with a group called the Breakthrough Listen Initiative, caution that although the signal had very particular qualities that set it apart from typical natural radio emissions, it will most likely turn out to be noise or interference caused by our own communication technology here on Earth, or even a natural phenomenon that has simply not been observed before. 

Still, at this moment, the possibility has not been ruled out for an intercepted alien transmission, so there’s still some space to let our imaginations play with the idea a bit. 


The Signal

The radio signal that has stirred up so much excitement was detected during observations of flares erupting from the red dwarf star Proxima Centauri, the smallest member of the triple Alpha Centauri system. At a distance of only 4.25 light years, Proxima Centauri is a stone’s throw away, astronomically speaking.

The signal was concentrated in a very narrow slice of the radio frequency spectrum, at 982 megahertz, which is typical of an artificial transmission. Signals from natural sources contain a wider mix of frequencies. Researchers listen for exactly this kind of narrow signal as they monitor star systems for any of non-natural, non-human origin.  

Artist concept of the surface of the super-Earth-sized exoplanet Proxima Centauri b, which orbits the red dwarf star Proxima Centauri within its habitable zone where it is warm enough for the existence of liquid surface water. We have no close-up pictures of this world, and whether water exists on its surface is yet unknown. (ESO/M.-Kornmesser/UNIGE)

It’s exciting to imagine that we have heard the radio whispers from extraterrestrial technology, whether it was a deliberate transmission aimed at us or merely ET’s television broadcasts drifting through space. Adding to the excitement, Proxima Centauri is known to possess at least two planets. One of them, a “super-Earth” called Proxima Centauri b, orbits within its star’s habitable zone, at the right distance for the star’s warmth to support liquid surface water and a potentially life-friendly environment. 

While researchers at Breakthrough Listen Initiative caution that with further analysis, the unusual signal will most likely turn out to be only radio interference from human technology — which has happened before — a final conclusion hasn’t been made. 

Breakthrough Listen Initiative

The Breakthrough Listen Initiative is a $100 million international effort to discover radio transmissions from extraterrestrial civilizations. Kicked off by Israeli-Russian billionaire Yuri Milner and Stephen Hawking in 2015, the Initiative is the most advanced and comprehensive ET-finding program humans have ever embarked on.  

The 10-year project will survey a million nearby stars, the entire plane of the Milky Way galaxy, and 100 nearby galaxies. The ambitious scale of these goals speaks loudly. There is still huge enthusiasm for answering the question: Is humanity alone in the cosmos, or do we share the galaxy with other intelligent, technological civilizations?

NASA's Transiting Exoplanet Survey Satellite (TESS), which is currently surveying the closest stars to our solar system for extrasolar planets. (NASA)

To help guide its search, the Breakthrough Listen Initiative is partnering with a NASA mission searching the nearest stars for extrasolar planets. The TESS spacecraft is expected to find thousands of exoplanets, including worlds the size of Earth, orbiting within their stars’ habitable zones. Targeting stars where TESS has discovered potentially life-friendly worlds improves the initiative’s chances of finding one with an intelligent, technological civilization. 

Search for Extraterrestrial Intelligence

Scientists have been using radio telescopes for decades to search for transmissions of intelligent origin, going back practically to the genesis of radio technology in the early 20th century. 

SETI, the Search for Extraterrestrial Intelligence, brought scientists together in the 1980s in a coordinated effort to detect ET radio signals, and was popularized in the 1997 movie "Contact," adapted from the novel by Carl Sagan. 

Piecing together the facts around Proxima Centauri and the unusual signal detected by the Parkes radio telescope, it’s tempting to envision some far-out possibilities. A seemingly artificial signal coming from the closest star system? An Earth-sized planet with an environment possibly friendly to life? The discovery excites the imagination. 

Even if the signal ultimately turns out to be a trick of our own technology, while there’s still a fleeting chance of a world-changing event like discovering extraterrestrial intelligence, we can enjoy a moment reveling in the possibility.