In 2019, a radio telescope in Australia detected an interesting signal coming from the vicinity of Proxima Centauri, the closest star to Earth.
The signal, designated Breakthrough Listen Candidate 1 (BLC1), had all the hallmarks of a 'technosignature', a potential sign of intelligent life.
It caught the imagination of researchers because the signal was a single identifiable wavelength (narrowband), had a Doppler shift (was moving), was localised on the sky and persisted for several hours.
All this suggested that the signal wasn’t due to a naturally occurring phenomenon.
Analysis revealed some problems with the extraterrestrial explanation, however. It turned out that the signal was also present in other observations of Proxima Centauri during the same period, but also (crucially) when the telescope wasn’t pointed at the star.
In similar observations the following year, the signal wasn’t detected at all. By analysing all the data captured by the Breakthrough Listen project, researchers later found similar signals from other targets, including blank sky. This means that the signal was almost certainly radio interference.
BLC1 is reminiscent of the so-called ‘Wow!’ signal, another narrowband radio signal detected in August 1977.
This potential ‘technosignature’ lasted a full 72 seconds and couldn’t easily be accounted for by a natural phenomenon.
Its precise location in the sky was never determined, though, and later searches of the area never saw the signal again.
Opinions differ on the source of the ‘Wow!’ signal, but there’s still no clear evidence that it was from an alien civilisation.
Signals aren’t the only alien signs scientists are looking out for, however.
Discovered in 2017, ‘Oumuamua (illustrated above) was an extremely elongated reddish rocky object spotted passing through the Solar System at colossal speed.
Its strange shape and trajectory caused some astronomers to speculate on whether the object was a ‘solar sail’ visiting from a distant alien civilisation.
But its odd properties could also be explained without invoking alien interference, so this is considered unlikely.
As of yet, scientists haven’t intercepted or detected anything that conclusively points to an exciting ‘alien’ origin.
This article is an answer to the question (asked by Daniel Howell, Leicester) 'Have we ever intercepted anything from aliens?'
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