Finding ET: New technique will narrow the search

In an extraordinary leap forward in the search for extraterrestrial intelligence (SETI), scientists have innovated a new method to discern and authenticate potential radio signals from other civilizations in our galaxy. 

This significant breakthrough could drastically improve our ability to validate future detections of extraterrestrial life.

Radio interference 

As of now, SETI searches primarily employ Earth-based radio telescopes, but these are susceptible to a myriad of ground and satellite radio interferences. 

From Starlink satellites to everyday domestic appliances such as cellphones and microwaves, to larger machinery like car engines, all can generate a radio blip which bears resemblance to the signature of an extraterrestrial civilization. 

False positives of this nature have led to countless disappointments since the inauguration of the first dedicated SETI program in 1960.

To confirm these signals, the existing practice involves shifting the telescope’s gaze to a different part of the sky and then returning multiple times to the original location of the signal detection. However, even this method does not entirely exclude the possibility of the signal being an unusual terrestrial occurrence.

Revolutionary technique 

Now, researchers at the Breakthrough Listen project at the University of California, Berkeley have developed a revolutionary technique. This method aims to determine whether the signal has truly traversed through interstellar space. This action eliminates any chance of Earth-based radio interference.

Breakthrough Listen holds the reputation for being the most comprehensive SETI search. The project extensively surveying the northern and southern skies for technosignatures.

It also targets thousands of individual stars situated in the Milky Way galaxy’s plane, the most plausible direction from which a civilization would transmit a signal, with a particular emphasis on the galaxy’s center.

Andrew Siemion, principal investigator for Breakthrough Listen and director of the Berkeley SETI Research Center (BSRC), lauded the advancement, saying, “I think it’s one of the biggest advances in radio SETI in a long time.” 

The Wow! signal

Siemion highlighted that this is the first technique capable of differentiating a single signal from radio frequency interference, a considerable feat, especially considering one-off signals like the famous Wow! signal.

The Wow! signal refers to a 72-second narrowband signal discovered in 1977 by an Ohio radio telescope, which appeared to differ significantly from any signal produced by normal astrophysical processes. 

So baffled by the discovery, the astronomer scribbled “Wow!” in red ink on the data printout. Despite intense scrutiny, observers have not detected the elusive signal since.

“The first ET detection may very well be a one-off, where we only see one signal,” said Siemion. He noted that without repetition, it’s challenging to draw any conclusions about a signal, with radio frequency interference being the most plausible explanation for such occurrences. 

“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.”

The research has been detailed in a study published in The Astrophysical Journal, authored by UC Berkeley graduate student Bryan Brzycki, Siemion, Brzycki’s thesis adviser Imke de Pater, UC Berkeley professor emeritus of astronomy, and colleagues at Cornell University and the SETI Institute in Mountain View, California.

Genuine ET signals

The team discovered that genuine signals from extraterrestrial civilizations should demonstrate attributes influenced by the ISM, which could help discriminate between Earth-based and space-based radio signals. 

The basis of this understanding comes from prior research describing how the ISM’s cold plasma, composed primarily of free electrons, affects signals from radio sources like pulsars.

Narrowband radio signals tend to rise and fall in amplitude over time — a phenomenon known as scintillation — due to refraction, or bending, caused by the intervening cold plasma. When these radio waves finally reach Earth via different paths, the waves interfere both positively and negatively.

New computer algorithm

Brzycki developed a computer algorithm that can analyze this scintillation and detect signals that dim and brighten over periods shorter than a minute, an indicator that they have passed through the ISM. 

“This implies that we could use a suitably tuned pipeline to unambiguously identify artificial emission from distant sources vis-a-vis terrestrial interference,” said Imke de Pater.

However, the technique is not without limitations. It will be useful only for signals that originate more than about 10,000 light years from Earth, as a signal must traverse through enough of the ISM to exhibit detectable scintillation. 

Any signal originating nearby would not exhibit this effect. Despite this, the development provides a robust new tool in our ongoing quest for contact with extraterrestrial life.

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