This has generated a flood of excitement in the press and among scientists themselves.
It has been dubbed Breakthrough Listen Candidate 1 or simply BLC-1.
The signal was present for the full observation, lasting several hours.
It also was absent when the telescope pointed in a different direction.
Artists impression of a planet orbiting Proxima Centauri.
Kornmesser/wikipedia,CC BY-SA
The signal was narrow-band, meaning it only occupied a slim range of radio frequencies.
And it drifted in frequency in a way that you would expect if it came from a moving planet.
In particular, BLC-1 highlights a problem that has dogged SETI research right from the beginning: disappearing signals.
BLC-1 hasnt been seen since it was first detected in the spring of 2019.
If BLC-1 finally emerges as a true SETI signal candidate, it will be the first since theWow!
signalrecorded back in 1977.
This is perhaps the most famous example of an inconclusive SETI candidate it was never observed again.
That doesnt mean it cannot be extraterrestrial in nature.
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This is especially the case for one-off events.
Ultimately, any one of them could potentially be the source of the BLC-1.
This should allow us to identify not just the stellar system but the associated planet that transmitted the signal.
In addition, radio interference from Earth wouldnt be registered by telescope sites separated by hundreds of kilometers.
This kind of interferometry is a well-established technique that has been around since the late 1960s.
So why are we not doing SETI with it systematically?
An observation of a few minutes would generate many terabytes of data (1 terabyte is 1,024 gigabytes).
Artists impression of the Square Kilometre Array.
Perhaps a more important factor is human inertia.
These scientists arent necessarily familiar with the quirks and foibles of interferometric arrays.
Luckily, thats finally changing.
In the meantime, prepare for a rising tide of ambiguous radio events and hopefully the reappearance of BLC-1.
Determining the precise location and motion of these signals may be the only way of reaching unequivocal conclusions.
