New analysis: The "Wow!" signal was much stronger than previously assumed

The famous and previously unexplained "Wow!" signal from 1977 was significantly stronger than previously assumed and could also have been observed by other observatories. This has been determined by a US research group on the basis of previously unpublished recordings and the findings have now been made public in advance. While a maximum flux density of 54 Jansky –, i.e. the incoming energy – (or, more rarely, 212 Jansky), had previously been assumed, the team has now determined a value of 250 Jansky. At the same time, the group assumes that the real value is likely to have been significantly higher. Only a few astrophysical sources are known to be the source of signals with such values, "so this event was exceptional".

Source in the solar system largely ruled out

The mysterious signal was recorded on September 15, 1977 with the "Big Ear" radio telescope at Ohio State University. The intensity surprised the responsible US astronomer Jerry Ehman so much that he scribbled around the string on the printout and wrote "Wow!" next to it. To this day, it remains unique and its origin unknown. Especially when it comes to the search for possible extraterrestrial civilizations ("SETI" for "Search for Extraterrestrial Intelligence"), the signal is cited again and again, as the research group now points out. Their new analysis was made possible by data that was digitized in a time-consuming process between 2006 and 2017. Based on this, they were able to recalibrate basic values of the Wow! signal, according to the team.

In the study, which has so far only been published on Arxiv and has not been independently verified, the group writes that the adjusted frequency of the signal of 1420.726 MHz suggests a significantly higher rotation of the source around itself. In addition, the determined speed of the source does not match that of most objects in the Milky Way, but there are exceptions with similar values. The values could also be explained by objects orbiting around others, such as exoplanets or gas clouds. The more precisely the frequency is known, the better possible sources can be ruled out. Finally, the frequency now determined also matches certain interstellar gas clouds, which have already been confirmed as the source of similar signals.

Based on the new values, the team has also adjusted the possible source region in the sky and at the same time confirmed once again that interference of terrestrial origin is highly unlikely to be the cause. The group has looked in detail at the possibilities that local radio interference, a so-called harmonic, satellites or space probes as well as artifacts in the data itself are the source of the signal. Solar activity can therefore also be ruled out as an explanation. As a possible astrophysical source, the research group also mentions a so-called maser, i.e. a naturally occurring laser in the microwave range. The team wants to investigate the historical data further.

Wow! signal was overlooked for a long time at the beginning

The research article also refers once again to the history of the signal, which initially failed to make waves despite the excitement of the discoverer. It was first mentioned in local newspapers, but only almost a year and a half after it was recorded and without its current name. It was only given this name on July 19, 1979 in an article in the Lima News from the town of the same name in Ohio. However, this did not attract much attention either. This only followed later in the summer after an article in the magazine Cosmic Search, which also contained the famous expression. Together with the films Star Wars and Close Encounters of the Third Kind and the two Voyager probes, the Wow! signal will celebrate its 50th birthday in two years' time.

(mho)