The 500-Meter Aperture Spherical Telescope (FAST), (aka. Tianyan, “Eye of Heaven”), is the largest radio observatory in the world. Since the observatory became operational in January 2020, this facility has made significant contributions to radio astronomy and the Search for Extraterrestrial Intelligence (SETI). In particular, the observatory has been instrumental in detecting Fast Radio Burts (FRBs) and other cosmic phenomena that could be (but probably aren’t) possible indications of extraterrestrial communications.
Last week, while sifting through FAST data, the China Extraterrestrial Civilization Research Group (CECRG) from Beijing Normal University revealed that they discovered several signals that might be artificial in origin (a possible indication of an advanced civilization). These signals consisted of narrow-band electromagnetic radio transmission and were considered one of the best candidates for an extraterrestrial signal. Ah, but there’s a snag. According to subsequent news releases, those radio transmissions were apparently from Earth!
Since the first SETI experiments began in the early 1960s (with Project Ozma), radio transmissions have remained the primary signature for which researchers have been looking. As the world’s largest and most sensitive radio telescope (even larger than the venerable Arecibo Observatory), FAST is the world’s premier radio facility dedicated to SETI research. One of its six main objectives* is to search the cosmos for possible technosignatures – i.e., indications of technological activity.
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To this end, Beijing Normal University, the National Astronomical Observatory of the Chinese Academy of Sciences (NAO/CAS), and the Berkeley SETI Research Center at UC Berkeley have partnered to create an international SETI research effort. In 2018, FAST took the first step by installing debugged back-end equipment to screen useful narrow-band candidate signals from background radio noise. By September 2020, the observatory officially began conducting science operations that included synchronous sky surveys and targetted exoplanet observations.
The team discovered two groups of “suspicious signals” that same year while processing data from the 2019 synchronic sky survey. This year, said CECRG team leader Professor Zhang Tongjie, the team found more possible radio signals while looking through data obtained during an exoplanet observation campaign. The Chinese state-affiliated news source Global Times shared the story on June 13th (since deleted), attesting to this discovery. As Prof. Zhang said in a statement to Chinese media:
“The possibility that the suspicious signal is some kind of radio interference is also very high, and it needs to be further confirmed and ruled out. This may be a long process. ‘China Sky Eye’ will repeat the observation of suspicious signals that have been discovered to further identify and detect new signals.”
Berkeley’s SETI Research Center, Dan Werthimer, who is part of the international collaboration and was involved in the survey, denied this a few days later. “The signals that we found so far are all [radio frequency] interference,” he said. “They’re not from extraterrestrials. They’re from terrestrials.” Werthimer has reportedly co-authored a preprint paper that details how the FAST findings were a false positive. Ironically, Prof. Zhang was correct when he suggested this but was incorrect when he said it might take a long time to confirm or deny it.
Such is the nature of SETI research, and the FAST observatory and its researchers should probably get accustomed to failure. It is, after all, the most likely outcome for those dedicated to searching for needles in the cosmic haystack, especially when we aren’t even sure what these needles will look like. As former NASA scientist and best-selling author David Brin once said about this field of research:
“Few important subjects are so data-poor, so subject to unwarranted and biased explanations – and so caught up in mankind’s ultimate destiny – than this one.”
There’s plenty of good news for those left feeling disappointed by this retraction. For example, the Japan Aerospace Exploration Agency (JAXA) just announced that their Hayabusa2 sample-return mission found no less than 20 strains of amino acids (the building blocks of DNA) on asteroid Ryugu. Second, the James Webb Space Telescope will be revealing its first images very soon and turning its infrared imaging capability toward several nearby exoplanets. The data it provides on these planets’ atmospheres could soon lead to a breakthrough in the search for habitable worlds beyond our Solar System!
In the end, all we can do is keep searching, waiting, and refining our methods. If there’s anyone out there also looking to answer the big question (“Are we alone?”), we’re sure to find them eventually.
*Other objectives include a large-scale neutral hydrogen survey, very long baseline interferometry (VLBI), probing the interstellar medium (ISM), pulsar observations, and timing.