A new technique is a dramatic breakthrough in the search for alien life, astronomers say.
Researchers at the Breakthrough Listen project based at the University of California, Berkeley say they have developed a new way to be sure that any potential signal is really coming from space – and not from something more boring.
Astronomers spend vast amounts of time looking for radio signals that might have come from alien civilisations as part of work on the search for extraterrestrial intelligence, or SETI. But they have in the past been fooled by very human technology, such as cellphones, microwaves and car engines, that can produce a blast of radio signals that look as if they have come from distant worlds.
One way to check whether signals are really alien is to point the telescope elsewhere and then repeatedly return to the same spot, with the hope of seeing the signal again and ensuring that it is not a false alarm. But that is not foolproof – and only works if the signal sticks around.
Some of the most promising radio signals might only be detectable once. The so-called “Wow!” signal, for instance – a radio signal detected in 1977 that was so shocking the astronomer who found it wrote the exclamation on a printout – has not been detected since, and astronomers still do not know whether it was an alien message or just a mistake.
Now scientists have devised a new test that can be used to see whether a signal has really passed through interstellar space, which should help show that it is not from elsewhere on Earth. It works by looking for “scintillation” – the changes in amplitude of a signal as it is affected by the cold plasma of space.
“The first ET detection may very well be a one-off, where we only see one signal. And if a signal doesn’t repeat, there’s not a lot that we can say about that. And obviously, the most likely explanation for it is radio frequency interference, as is the most likely explanation for the Wow! signal,” said Andrew Siemion, principal investigator for Breakthrough Listen and director of the Berkeley SETI Research Center, which operates the world’s longest running SETI program.
“Having this new technique and the instrumentation capable of recording data at sufficient fidelity such that you could see the effect of the interstellar medium, or ISM, is incredibly powerful.”
Dr Siemion called the breakthrough “one of the biggest advances in radio SETI in a long time” and said that it would be the first time researchers would be able to differentiate a real signal from a false alarm, even if it was only detected once.
The technique can only be used for signals that have travelled 10,000 light years or more to Earth, researchers note. If it was closer to us, the scintillation effect cannot be seen because they are not travelling through enough of the interstellar medium, or ISM.
The research is described in a new paper, ‘On Detecting Interstellar Scintillation in Narrowband Radio SETI’, published in The Astrophysical Journal.
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