Professor Abel Méndez, Director of the Planetary Habitability Laboratory and a planetary astrobiologist at the University of Puerto Rico, and colleagues may have solved the mystery of the ‘strange’ signal — dubbed the ‘Weird!’ Signal — from the nearby star Ross 128. According to the team, the best explanation is that the signal is a broadband radio transmission from one or more Earth-orbiting artificial satellites.
Ross 128 (center), also known as HIP 57548 or IRAS 11451+0105, is a red dwarf star. It has 15% of the mass of the Sun and 21% of the Sun’s radius, but generates energy so slowly that it has only 0.036% of the Sun’s visible luminosity. Image credit: Sloan Digital Sky Survey.
On May 12, 2017, Professor Mendez and co-authors observed a group of nearby red dwarf stars (Ross 128, Gliese 398, Gliese 436, Wolf 359, HD 95735, BD +202465, and K2-18) with the 305-m (1,000-foot) radio telescope at the Arecibo Observatory, Puerto Rico.
The astronomers detected an anomalous radio signal during the observation of Ross 128, a low-mass red dwarf and one of the nearest stars to the Sun at a distance of only 10.96 light-years. The signal lasted for around 10 min and was in frequencies between 4.6 and 4.8 GHz.
They proposed three main explanations for the source of the strange signal: (i) unusual stellar activity; (ii) emissions from other background objects; or (iii) interference from satellite communications.
“Each of these potential solutions has its own problems, and so the mystery here was that we were not able to accurately distinguish between these working hypotheses,” Professor Méndez explained.
“There were other less likely possibilities, such as ground radio interference, data processing errors, among several others.”
The Weird! Signal. Instead of emanating from Ross 128, the most likely source of the signal is a satellite orbiting the Earth. Image credit: Planetary Habitability Laboratory, University of Puerto Rico.
“However, many people were more interested in the signals as potential proof of transmissions from an extraterrestrial intelligent civilization,” he said.
“Statistically, this is always the last consideration, not because such civilizations are impossible, we humans are an example, but because other possibilities had frequently arisen and no extraterrestrial civilizations have been detected yet.”
He added: “other unexplained signals, like the Wow! Signal, are commonly cited outside of academia to be proof of extraterrestrial communications. Unexplained here does not mean inexplicable; it just means we are not able to tell which is the precise source from many possibilities.”
“This was precisely the case of our signal from Ross 128, which we now call the Weird! Signal.”
“We discussed our results with many other radio astronomers, but came up with no definitive answers. This finally motivated us to request the help from SETI Berkeley and the SETI Institute teams.”
The new observations of Ross 128 were carried out on July 16, 2017, with the Arecibo Telescope.
The Breakthrough Listen science team at the University of California, Berkeley’s SETI Research Center joined in this campaign and simultaneously observed the star using the Green Bank Telescope (GBT).
Position of known Earth-orbiting satellites with radio transmitters operating between 4-8 GHz; the location of Ross 128 is ra=177 degrees, dec=1 degree. Image credit: Enriquez et al.
“After a careful analysis of the observations we performed last Sunday from the Arecibo Observatory, together with SETI Berkeley using the GBT and the SETI Institute’s Allen Telescope Array, we are now confident about the source of the Weird! Signal,” Professor Méndez said.
“The best explanation is that the signals are transmissions from one or more geostationary satellites.”
“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.”
“This fact, though, does not yet explain the strong dispersion-like features of the signals; however, it is possible that multiple reflections caused these distortions, but we will need more time to explore this and other possibilities.”
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Abel Mendez et al. 2017. The Weird! Signal.
J. Emilio Enriquez et al. 2017. Breakthrough Listen Follow-up of the Reported Transient Signal Observed at the Arecibo Telescope in the Direction of Ross 128.
