The Breakthrough Listen project, part of the Search for Extraterrestrial Intelligence (SETI), has detected a radio signal they have yet to be able to explain. It comes from a part of the sky that includes Proxima Centauri. To the annoyance of many involved, news leaked while analysis is still ongoing, leading to some epic conclusion jumping. Those studying the data stress the chance of this being the output of an alien civilization is very low, but isn't zero, unlike every radio sample we've seen since 1977.
More than a year ago, the Parkes Radio telescope detected radio waves at a frequency of 982 megahertz five times in the course of three hours. The famous dish picks up so much material that analysis is often delayed. It was only this October that Breakthrough intern Shane Smith noticed how unusual this round was.
Radio detections from natural sources are typically smeared across a wide range of wavelengths. This one, however, was only observed in the one frequency range. “We don’t know of any natural way to compress electromagnetic energy into a single bin in frequency” Dr Andrew Siemion of the University of California, Berkeley told Scientific American.
Radio telescopes frequently pick up signals that don't look like they can be natural, but are quickly shown to be coming either from Earth, or from humanity's satellites. One of the Parkes telescope's stranger detections was eventually revealed to be from the premature opening of the facility's microwave oven.
However, 982 MHz is a little-used part of the spectrum, and the slightly rising frequency is unusual for a terrestrial source.
Since the discovery, Breakthrough researchers have been carefully investigating, checking for possibilities of instrument error, satellites broadcasting at 982 MHz, or a natural phenomenon with uniquely tight emissions frequencies. So far they have found no alternative explanation, but they're still looking.
Breakthrough Listen was not planning to announce the detection until further analysis had been conducted. Instead, news leaked last week, leading to the response through the Scientific American article. Full details have not yet been released, but we know nothing similar has been detected since.
Naturally, with no alternative explanations available, people's minds jump to the possibility of aliens – the reason Breakthrough Listen is listening to the sky in the first place. Nevertheless, these things often take time, which the leak cut short. Breakthrough's Peter Worden told Scientific American; “The most likely thing is that it’s some human cause. And when I say most likely, it’s like 99.9 [percent].” On Twitter, Worden sounded frustrated.
Terminology exacerbates the problem. Radio astronomers refer to anything besides random noise, like that from a definitely uninhabitable planet last week, as a signal. For those outside the field, however, the word implies a deliberate message.
The signal was detected in the course of Parkes' study of flares on Proxima Centauri – the same stellar activity many astronomers think make planets around the Sun's nearest neighbor unsuited to life. That doesn't, however, mean the source is in our galactic neighborhood. We just know it is within 16 arcminutes of Proxima, an area that includes many more distant stars. There could be many sources of similar signals – whether natural or alien – across the galaxy, and we only picked up this one because there's a target star in the same part of the sky.
Nevertheless, if by some chance this is from aliens, a source orbiting Proxima would raise the immense significance even higher. Most stars are so distant that travel, or even communication, would require hypothetical concepts like warp drive or ansibles.
Proxima, however, is close enough people are already tinkering with plans to send probes, and messages could get replies in less than nine years.