The Weird! Signal
Last week we distributed a press release announcing the Planetary Habitability Laboratory’s new collaboration with other observatories to study the
red dwarf stars Barnard’s Star and Ross 128. We wanted to observe Barnard’s Star because it is a nearby star that might have planets and is
currently being observed by the Red Dots project. We also wanted to observe, again, Ross 128 because in our previous observing campaign performed in
May 2017 using the Arecibo Observatory we detected some peculiar signals from this star. Our project using the Arecibo Observatory, the world’s most
active and most sensitive single-dish radio telescope, was originally aimed at searching for radio emissions from red dwarf stars intended to
understand their stellar activity and any star-planet interactions.
Our follow-up observations of Ross 128 got much more attention from the press than we expected, although not necessarily for the right reasons. Based
on our observations, we proposed three main explanations for the source of the strange signals from the star: (1) unusual stellar activity, (2)
emissions from other background objects, or (3) 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. There were other less likely possibilities, such as ground radio interference, data processing errors, among several others.
However, many people were more interested in the signals as potential proof of transmissions from an extraterrestrial intelligent civilization.
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. Nevertheless, scientists need to be open to all
possibilities and explore them. The Search for Extraterrestrial Intelligence (SETI) is a field of research that is part of astrobiology, and as such
pursues finding signatures of life elsewhere in the galaxy. The SETI Berkeley Research Center at the University of California, and the SETI Institute
are experts in this field.
There are many other examples where strange signals detected from different observatories resulted in the discovery of new astronomical phenomena or
had a mundane explanation. For example, pulsars, which were originally referred to as LGM (Little Green Men), are fast rotating neutron stars. Peryton
observations at Parkes Observatory in Australia were later shown to be caused by a malfunctioning microwave oven. Other strange signals are still a
mystery, such as the recently detected Fast Radio Bursts (FRB), which the Arecibo Observatory helped to confirm and was essential in establishing
their extragalactic origin.
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;
both of which have a lot of observational experience and know very well the various kinds of terrestrial radio emissions.
Given the attention the story received from the media, we launched a public survey to ask people on the possible explanations of the Weird! Signal.
The purpose of this survey was not in any sense to try to solve the mystery, but to involve the public in the excitement of real-time science.
Nine possible explanations for the Weird signal were given to the public in the survey: (1) stellar activity, (2) other astronomical source, (3) a
satellite, (4) local interference, (5) instrumental glitch, (6) error in data acquisition, (7) error in data processing or calibration, (8) pattern in
noise or (9) signal from aliens (a tenth possibility, “other explanation” was also included).
Nearly 800 people participated in this informal survey (including more than 60 astronomers); the consensus was that the most likely explanation was
either (1) or (2), namely an astronomical phenomenon (see figure below). Causes related to radio interference or instrumental failures were considered
most unlikely. This is interesting since in the absence of solid information about the signal, most astronomers would think that these would probably
be the most likely explanation.
Also interesting is the fact that a non-negligible number of participants in the Survey (~200) thought the most likely explanation of the signal was
that of a communication with an Extraterrestrial Intelligence (ETI). However, a similar number thought that this would only happen “in our craziest
dreams”. Although we do not necessarily share none of these opinions, these results reflect the still high expectations the public has on the
possibility of contacting ETI.
After a careful analysis of the observations we performed last Sunday from the Arecibo Observatory, together with SETI Berkeley using the Green Bank
Telescope and the SETI Institute’s Allen Telescope Array, we are now confident about the source of the Weird! Signal. 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 (diagonal lines in the figure); however, It is possible that multiple
reflections caused these distortions, but we will need more time to explore this and other possibilities.
The Planetary Habitability Laboratory of the University of Puerto Rico at Arecibo made many new friends from this experience. We started coordinating
efforts with the Red Dots team on their search for planets around nearby stars. We had the cooperation of AAVSO and other observatories with follow-up
observations. Our students from the University of Puerto Rico could be involved in the scientific process, attending observations at the Arecibo
Observatory and conducting data reduction. Such an experience is invaluable to our future scientists.
Finally, this was a great experience of open science. 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.