Global Affairs

Opinion: Why astronomers are interested in this mysterious signal

And indeed, a recent report of a transmission originating from Proxima Centauri, the closest star to our own, was reported by the British newspaper The Guardian in December. The source of the story is not a scientific paper, but instead seems to have been leaked by an anonymous source. The claim of an intercepted signal, if it turns out to be truly sign of extraterrestrial intelligence, would be one of the most momentous discoveries of all times. But this reported signal is almost certainly not that.
In April and May of 2019, the 64-meter-wide Parkes radio telescope, located in Australia, was recording radio transmissions from the direction of nearby star Proxima Centauri. Over the course of hours, the telescope recorded data from the star for 30-minute intervals, before steering away to look at a different direction. This procedure, called “nodding,” is used to establish that any observed signal is coming from a particular direction, rather than just random radio noise. For five of these half-hour intervals, the signal was observed while the antenna was pointing at Proxima Centauri, and it was not detected at all when it was aimed in another direction.
This signal was not immediately noticed; it was over a year after the data was recorded that Shane Smith, an intern with Breakthrough Listen, a project funded by billionaire Yuri Milner that seeks to find signals of extraterrestrial life, found it buried in the telescope’s recordings. This was in late October 2020.
So, what, exactly was seen? It was a radio signal at a single frequency, specifically 980.002 MHz. The signal drifted slightly with time, which is what you’d expect if it was emitted by a planet or moon orbiting a star. It was observed to have originated in a small patch of the sky, about half the diameter of the full moon, centered on Proxima Centauri.

First and foremost, it is important to note that astronomers think it is highly unlikely that the signal is caused by space aliens trying to communicate with us. Even the researchers involved in Breakthrough Listen do not make that claim.

It is also important to remember that this observation has not yet been published in a refereed journal, so it has not undergone rigorous scientific review. Instead, the internet buzz arose from a rumor of the signal that was leaked to The Guardian, which published it on December 18.
Still, it is interesting to do the thought experiment about whether the signal was really a communication from a civilization orbiting around a distant star. Proxima Centauri is our astronomical neighbor, just 4.2 light years away. It is a red dwarf star, so dim that it is not visible to the human eye. Proxima Centauri is known to have at least two planets. One is about seven times the mass of Earth, while the other is only about 20% more massive than Earth. The smaller planet orbits very close to the star, circling it in a mere 11 days.
Proxima Centauri is dim compared to the Sun, and this smaller planet is located the right distance away from its star to possibly have liquid water. It is in what is called the Goldilocks zone — not too hot, not too cold, but just right.
This makes the planet an exciting one for astronomers to study. A radio signal from a possibly habitable world could be the first proof that we are not alone in the universe. But we shouldn’t be hasty. For one thing, the smaller planet orbiting Proxima Centauri is close enough to be affected by sudden bursts of energy called flares from the parent star. These flares would likely both bathe the planet with enough radiation to kill any familiar form of life and also strip away any possible atmosphere. The planet would also be “tidally locked,” with one face always facing the star, much like we see only one face of the Moon. It turns out that this planet is very unlikely to be a pleasant place.

In addition, it is simply much more likely that the radio signal is of terrestrial origin. We live in a world of radio signals, from AM and FM broadcasts of current music hits to cell phones and errant emissions from microwave ovens. And, with its frequency of 980.002 MHz, it’s very curious that the signal frequency happens to be so close to an integer. If this is a signal from alien life, this would suggest it counts time in seconds the way we do. Plus, the signal is a single frequency. Radio transmissions need to vary in strength or frequency to transmit information, and this one doesn’t, so if it is an alien trying to communicate, they’re clearly not trying to tell us much.

So, sadly, it’s likely that this potentially exciting signal has an ordinary cause. But that is quite beside the point. The important thing is that, whether it was generated by aliens or not, humanity detected the signal. We are gazing out into the cosmos, actively looking to see if we have cosmic neighbors. And that is good. It is something we should be doing.

One day, that scene acted out in “Contact” will be real. Some researcher will be surprised by a faint and scratchy signal from the sky — a signal that will change everything. But only if we’re listening. When ET does make that call, someone should be manning the phones.

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