The Arecibo Observatory Reveals New Explanation for the Wow! Signal
Researchers from the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo have proposed a compelling explanation for one of the most enigmatic radio signals ever detected—the Wow! Signal. Originally captured in 1977 by the Ohio State University’s Big Ear radio telescope, the Wow! Signal has long puzzled scientists as a potential sign of extraterrestrial intelligence due to its strong intensity and narrow bandwidth near the 1420 MHz hydrogen line.
The new research, led by Abel Méndez, marks the first phase of the "Arecibo Wow!" project, an ambitious endeavor to search for similar signals using archived data from the former Arecibo Observatory. From 2017 to 2020, the team observed various celestial targets at frequencies ranging from 1 to 10 GHz using the observatory's iconic 305-meter telescope. In 2023, the project continued with observations at 8 GHz using a 12-meter telescope, focusing on red dwarf stars with potentially habitable planets.
“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,” said Méndez.
The research proposes that the Wow! Signal may have been caused by a unique astrophysical event: the sudden brightening of a cold hydrogen cloud due to stimulated emission from a transient strong radiation source, such as a magnetar flare or a soft gamma repeater (SGR). These rare events might cause hydrogen clouds to momentarily shine much brighter, potentially explaining the fleeting nature of the Wow! Signal.
This hypothesis not only accounts for the unique characteristics of the Wow! Signal but also highlights a new source of false positives in the search for extraterrestrial technosignatures. “Our study suggests that the Wow! Signal was likely the first recorded instance of maser-like emission of the hydrogen line,” added Méndez. This hypothesis may redefine our understanding of such signals and guide future searches for extraterrestrial life.
Furthermore, the exact origin of the Wow! Signal, or similar events, may be pinpointed by examining the background stellar objects within or beyond these cold hydrogen clouds.
The study, titled 'Arecibo Wow! I: An Explanation for the Wow! Signal,' is currently being refined based on feedback from the scientific community and will soon be submitted for peer review to an astrophysical journal." For further information, visit the project page phl.upr.edu/wow.
Cold hydrogen clouds in the galaxy emit faint narrowband radio signals similar to those shown here, detected by the Arecibo Observatory in 2020. A sudden brightening of one of these clouds, triggered by a strong emission from another stellar source, may explain the Wow! Signal.
About the Arecibo Observatory
The Arecibo Observatory, until its collapse in 2020, was one of the world’s largest and most powerful radio telescopes. It contributed to numerous groundbreaking discoveries in radio astronomy, atmospheric science, and planetary radar. The observatory continues to be remembered for its significant contributions to studying the universe.
About the Planetary Habitability Laboratory
The Planetary Habitability Laboratory (PHL) at the University of Puerto Rico at Arecibo is dedicated to the study of planets around other stars. The laboratory’s research focuses on the conditions allowing habitable environments and the potential for life beyond Earth.