New Radio Technique Raises Hopes for Detection of Alien Life in the Galaxy

Wednesday - July 19 2023, 21:20 UTC - 1 year ago

The search for extraterrestrial life (SETI) involves looking for ‘technosigatures’ from aliens, but Earth noise can make this difficult. The new technique devised by the Breakthrough Listen project enables radio-wave monitors to more easily differentiate between signals from deep space and human-made interference and could revolutionize the search for alien life.

A new technique for parsing radio data from telescope arrays is raising hopes among astronomers that a breakthrough in the hunt for alien life in the galaxy is on the horizon. The search for extraterrestrial life (SETI) currently involves trying to detect ‘technosigatures’ from aliens, principally by looking for narrow-band radio signals that an alien civilization might be sending out. The problem, of course, is that humans on Earth are also broadcasting an incredible number of radio signals, including narrow-band signals. As such, Earth noise, including everything from car engines to Starlink satellites, creates a kind of white noise filter around the Earth that is extremely hard for an alien radio signal to stand out from, especially considering that it has likely traveled hundreds if not thousands of light-years to reach us, and so would be extremely faint.

Now, researchers at the University of California, Berkeley’s Breakthrough Listen project say they’ve found a way to pull these cosmos signals out of the noise of terrestrial interference, and it could revolutionize the search for alien life.

"I think it’s one of the biggest advances in radio SETI in a long time," Andrew Siemion, principal investigator for Breakthrough Listen and director of the Berkeley SETI Research Center (BSRC), which operates the world’s longest running SETI program, said in a UC-Berkeley statement. "It’s the first time where we have a technique that, if we just have one signal, potentially could allow us to intrinsically differentiate it from radio frequency interference. That’s pretty amazing, because if you consider something like the Wow! signal, these are often a one-off." .

The Wow! signal, an especially powerful radio signal spotted by an astronomer in 1977 that many hoped would be the beginning of human-alien communication, has never been repeated, and its source is still a subject of intense debate. The search for repeating signals from an identifiable source, meanwhile, is currently the only way we have to potentially spot alien signals amid the cacophony of Earth. It’s a time-consuming process, and even if follow-up signals are detected, the signal doesn’t necessarily mean aliens; it could be the result of some unknown phenomena.

That’s what makes the new technique, described this month in The Astrophysical Journal, so thrilling. The way the new technique works is by looking for scintillation — a repeated brightening and dimming of the signal’s amplitude — in the radio signals hitting our radio telescopes.

Previous research found that radio signals from objects like pulsars would be affected by the cold plasma of the interstellar medium, warping and bending the radio signal so that when the radio waves eventually reach Earth, the distortion along the way produces positive and negative interference patterns in the signals or scintillations. The important leap that Siemion and his colleagues made however is that these scintillations would also affect the very narrow-band radio signals that SETI has been looking for since the 1960s. Since these scintillating signals are definitionally coming from intersteller sources, rather than terrestrial sources, this means that radio-wave monitors can more easily differentiate between signals from deep space and human-made interference.