The "Wow!" signal was originally captured in 1977 by the Ohio State University’s Big Ear radio telescope (Credit: Big Ear Radio Observatory and North American AstroPhysical Observatory)
ARECIBO, Puerto Rico — For nearly half a century, astronomers have been puzzled by a brief and unexplainable radio signal detected in 1977 that seemed to hint at the existence of alien life. Known as the “Wow! Signal,” this tantalizing cosmic transmission has remained one of the most intriguing mysteries in the search for signs of intelligent life in outer space. Now, scientists may finally know where it came from!
A team of researchers may have uncovered a potential astrophysical explanation for the Wow! Signal that could reshape our understanding of this enduring enigma. Their findings, currently published in the preprint journal arXiv, suggest the signal may have been the result of a rare and dramatic event involving a burst of energy from a celestial object interacting with clouds of cold hydrogen gas in the Milky Way galaxy.
“Our latest observations, made between February and May 2020, have revealed similar narrowband signals near the hydrogen line, though less intense than the original Wow! Signal,” explains Abel Méndez, lead author of the study from the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo, in a media release.
“Our study suggests that the Wow! Signal was likely the first recorded instance of maser-like emission of the hydrogen line.”
The Wow! Signal was detected by the Big Ear radio telescope at The Ohio State University on August 15, 1977. It exhibited several intriguing characteristics, including a narrow bandwidth, high signal strength, and a frequency tantalizingly close to the natural radio emission of neutral hydrogen — an element abundant throughout the universe. These properties led many to speculate the signal could be of artificial origin, perhaps a deliberate message from an extraterrestrial intelligence.
This passing burst of activity in space led Dr. Jerry Ehman to famously write “Wow!” next to the print-out of the signal, which was like nothing else astronomers were seeing in space at the time. However, the signal was never detected again, despite numerous attempts to locate its source over the ensuing decades.
This has posed a major challenge for the SETI (Search for Extraterrestrial Intelligence) community, as repetition is considered essential for verifying the authenticity of a potential extraterrestrial signal — also known as a technosignature.
This new study, however, is pushing the conversation away from an alien radio transmission and closer to a once-in-a-lifetime natural occurrence in deep space. The researchers’ key insight stems from observations made using the now-decommissioned Arecibo Observatory in Puerto Rico, one of the world’s most powerful radio telescopes until its collapse in 2020.
For now, the Wow! Signal remains shrouded in mystery, but there is now at least a plausible explanation for its existence — one that does not involve aliens.
Paper Summary
Methodology
Between 2017 and 2020, the researchers conducted a series of observations targeting red dwarf stars – small, dim stars that are the most common type in the Milky Way. Their observational strategy was not specifically tailored to detecting technosignatures, but rather aimed at studying the radio emissions from these active stellar systems and their potentially habitable exoplanets.
During these observations, the team noticed the presence of several narrow-band radio signals near the hydrogen line frequency, similar to the characteristics of the Wow! Signal. However, these signals were much weaker in intensity compared to the original Wow! detection.
Key Results
Upon closer analysis, the researchers determined that these weaker signals were not associated with the red dwarf stars themselves but rather with nearby clouds of cold hydrogen gas in the galaxy. They hypothesize that the Wow! Signal may have been caused by a rare, transient event that temporarily amplified the brightness of one of these hydrogen clouds, resulting in the intense, narrow-band detection observed by the Big Ear telescope.
The team proposes that the trigger for this dramatic brightening could have been a powerful cosmic event, such as a flare from a highly magnetized neutron star known as a magnetar — or a sudden burst of energy from a soft gamma-ray repeater (SGR) — a type of extremely energetic stellar object.
Study Limitations
While the researchers believe their hypothesis offers a plausible explanation for the Wow! Signal, they acknowledge that it remains speculative and will require further observational evidence to be conclusively proven. The transient nature of the proposed event and the precise alignment required between the cosmic source, hydrogen cloud, and Earth’s vantage point make it inherently challenging to reproduce the Wow! Signal conditions.
Discussion & Takeaways
If the researchers’ hypothesis is correct, it would have significant implications for the search for technosignatures. It suggests that some narrow-band radio signals previously considered potential markers of alien technology may actually be the result of natural astrophysical phenomena, like the interaction between cosmic events and interstellar gas clouds.
“The implications of these findings are significant for SETI research. They highlight the need for continuous long-term monitoring strategies and developing more sensitive detection technologies. The study also stresses the importance of revisiting and re-analyzing historical datasets with newer, more advanced technology, which could potentially uncover subtleties missed in earlier analyses,” the team writes in their report.
The researchers plan to continue their Arecibo Wow! project, exploring the extensive archival data from the now-defunct observatory to search for additional examples of these hydrogen cloud-based signals. They also hope to use high-resolution radio telescopes like the Very Large Array to pinpoint the precise location of the original Wow! Signal, which could help identify the specific cosmic event that triggered its detection.
Funding & Disclosures
This research was funded by the National Science Foundation and the University of Puerto Rico at Arecibo. The authors declare no conflicts of interest.
