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hubie [soylentnews.org] writes:

Scientists have devised a new technique for finding and vetting possible radio signals from other civilizations in our galaxy [berkeley.edu]:

Most of todays SETI searches are conducted by Earth-based radio telescopes, which means that any ground or satellite radio interference ranging from Starlink satellites to cellphones, microwaves and even car engines can produce a radio blip that mimics a technosignature of a civilization outside our solar system. Such false alarms have raised and then dashed hopes since the first dedicated SETI program began in 1960.

Currently, researchers vet these signals by pointing the telescope in a different place in the sky, then return a few times to the spot where the signal was originally detected to confirm it wasn't a one-off. Even then, the signal could be something weird produced on Earth.

The new technique, developed by researchers at the Breakthrough Listen project at the University of California, Berkeley, checks for evidence that the signal has actually passed through interstellar space, eliminating the possibility that the signal is mere radio interference from Earth.

[...] I think its one of the biggest advances in radio SETI in a long time, said Andrew Siemion, principal investigator for Breakthrough Listen and director of the Berkeley SETI Research Center [berkeley.edu] (BSRC), which operates the worlds longest running SETI program. Its 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. Thats pretty amazing, because if you consider something like the Wow! signal, these are often a one-off.

Siemion was referring to a famed 72-second narrowband signal observed in 1977 by a radio telescope in Ohio. The astronomer who discovered the signal, which looked like nothing produced by normal astrophysical processes, wrote Wow! in red ink on the data printout. The signal has not been observed since.

The first ET detection may very well be a one-off, where we only see one signal, Siemion said. And if a signal doesnt repeat, theres 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. 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.

[...] Siemion noted that, in the future, Breakthrough Listen will be employing the so-called scintillation technique, along with sky location, during its SETI observations, including with the Green Bank Telescope in West Virginia the worlds largest steerable radio telescope and the MeerKAT array in South Africa.

[...] This implies that we could use a suitably tuned pipeline to unambiguously identify artificial emission from distant sources vis-a-vis terrestrial interference, de Pater said. Further, even if we didnt use this technique to find a signal, this technique could, in certain cases, confirm a signal originating from a distant source, rather than locally. This work represents the first new method of signal confirmation beyond the spatial reobservation filter in the history of radio SETI.

[...] The technique will be useful only for signals that originate more than about 10,000 light years from Earth, since a signal must travel through enough of the ISM to exhibit detectable scintillation. Anything originating nearby the BLC-1 signal, for example, seemed to be coming from our nearest star, Proxima Centauri would not exhibit this effect.

Journal Reference:
Bryan Brzycki et al 2023 ApJ 952 46 DOI 10.3847/1538-4357/acdee0 [doi.org]

Original Submission