In the early hours of August 15, 1977, volunteer astronomer Jerry R. Ehman examined printouts from Ohio State University’s Big Ear telescope and spotted an anomalous sequence—"6EQUJ5"—peaking nearly 30σ above background. He circled it and scribbled “Wow!”, instantly immortalizing one of SETI’s most tantalizing enigmas.
The signal occupied a narrow band around 1420.4556 MHz—the hydrogen line—lasted exactly 72 seconds (the time Big Ear could observe a fixed point), and has never recurred despite extensive follow-ups.
Detection and the “Wow!” Moment
Big Ear’s design relied on Earth’s rotation to sweep its dual beams across the sky. The Wow! Signal’s rise-and-fall intensity matched the beam profile perfectly, suggesting a point source. Coordinates fell near Sagittarius, but the telescope’s dual-horn setup left two possible right ascensions.
Search for Repeats and Follow-Ups
Astronomers scoured archival data and dedicated time on the Very Large Array, Green Bank Telescope, and Allen Telescope Array. None recorded a second transmission, and the signal’s uniqueness left no corroborating observations.
Leading Hypotheses
Legacy in SETI
The Wow! Signal spurred improvements in narrowband search techniques, influenced the design of Cooper vanes to secure aircraft, and inspired modern initiatives like Breakthrough Listen to scan billions of channels with AI-driven analysis.
More than four decades later, the Wow! Signal remains a beacon of cosmic mystery—proof that even a fleeting whisper from the stars can ignite humanity’s enduring quest for extraterrestrial life.