The Search for Extraterrestrial Intelligence (SETI) aims to answer one of the most important scientific questions: are we alone in the Universe? Complementing other subfields of astrobiology in the attempt to detect extraterrestrial life, radio SETI strives to detect and constrain the existence of technosignatures, signals that betray the presence of intelligent extraterrestrial civilizations. The newly-developed SETI technique checks for evidence that the radio signal has actually passed through interstellar space, eliminating the possibility that the signal is mere radio interference from Earth.
CSIRO’s Parkes radio telescope in New South Wales, Australia. Image credit: Shaun Amy.
Most of today’s SETI searches are conducted by Earth-based radio telescopes, which means that any ground or satellite radio interference can produce a radio blip that mimics an alien technosignature.
Such false alarms have raised and then dashed hopes since the first dedicated SETI program began in 1960.
Currently, SETI astronomers 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 checks for evidence that the signal has actually passed through interstellar space, eliminating the possibility that the signal is mere radio interference from Earth.
It was developed by astronomers at the Breakthrough Listen project at the University of California, Berkeley.
“I think it’s one of the biggest advances in radio SETI in a long time,” said Breakthrough Listen project principal investigator Dr. Andrew Siemion, director of the Berkeley SETI Research Center.
“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.”
“I’m referring to a famed 72-second narrowband signal observed on August 15, 1977 by a radio telescope in Ohio.”
“The first ET detection may very well be a one-off, where we only see one signal,” Dr. Siemion said.
“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.”
“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 is incredibly powerful.”
“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 and the MeerKAT array in South Africa.”
The team’s technique is described in a paper in the Astrophysical Journal.
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Bryan Brzycki et al. 2023. On Detecting Interstellar Scintillation in Narrowband Radio SETI. ApJ 952, 46; doi: 10.3847/1538-4357/acdee0
