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Weird Signal at Arecibo
The “Weird! Signal” from Ross 128, detected on May 12, is highlighted by the red box in this chart of frequency signal strength over time. (PHL @ UPR Arecibo)

A week ago, astronomers using the Arecibo radio telescope in Puerto Rico were intrigued about a radio signal they picked up in May, apparently from the vicinity of the red dwarf star Ross 128. Now they think they know what it was.

Spoiler alert: It’s not aliens.

To gather more evidence about the source of the quasi-periodic signal, astronomers took a closer look at the star last Sunday – not only with the 1,000-foot-wide Arecibo Observatory, but with the Green Bank Telescope in West Virginia and the SETI Institute’s Allen Telescope Array in California.

“We are now confident about the source of the ‘Weird! Signal,'” Abel Mendez, a planetary astrobiologist at the University of Puerto Rico at Arecibo, said today in an update.

“The best explanation is that the signals are transmissions from one or more geostationary satellites,” Mendez wrote. “This explains why the signals were within the satellite’s frequencies, and only appeared and persisted for Ross 128; this star is close to the celestial equator where many geostationary satellites are located.”

Ross 128 is nearly 11 light-years from Earth in the constellation Virgo. (PHL @ UPR Arecibo / Aladin Sky Atlas)

There are still some questions to be resolved. Mendez said the satellite scenario doesn’t explain why the signals exhibited a strong dispersion-like pattern.

“It is possible that multiple reflections caused these distortions, but we will need more time to explore this and other possibilities,” he said.

Mendez and his colleagues call the original transmission they detected the “Weird! Signal,” as a tribute to an anomalous radio flash known as the “Wow! Signal.” That strong narrow-band signal was picked up in 1977 years ago and went unexplained for nearly 40 years. This year, astronomers published a paper proposing that the Wow Signal was caused by a cometary cloud.

In the case of the Weird Signal, satellite transmissions were suggested as one possible explanation from the beginning, but it took additional data to strengthen the case. Aliens were never seriously considered, although that angle is why Ross 128 got far more attention than Mendez expected.

It would have been exciting to find evidence for an exotic phenomenon at Ross 128, on a par with the discovery of pulsars or fast radio bursts. But Mendez doesn’t sound disappointed.

“This was a great experience of open science,” Mendez said. “Sometimes projects, observational campaigns or missions do not necessarily reach their objectives. The lesson here is that we all need to continue exploring and sharing results openly. Some people prefer to only learn about the successes, but others prefer science in real time, no matter the end result.”

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