The Wow! signal

The claim

"A 72-second radio burst was the best alien signal ever received."

Where the idea comes from

Astronomer Jerry Ehman circled the printout of a strong narrowband signal near the hydrogen line and wrote "Wow!".

What the evidence shows

1. The signal rose and fell over 72 seconds, exactly how a fixed point in the sky would pass through the telescope's beam as Earth turned.
2. It was near 1420 MHz, the frequency SETI researchers expected aliens might use.
3. It has never been detected again despite dozens of searches, which makes it impossible to test.
4. A 2024 study proposed a rare natural cause: a cold hydrogen cloud suddenly brightened by a flare from a magnetar, similar signals having been seen in archival data.

What is still open

A one-off can never be confirmed. If a similar signal repeated, it could be studied properly.

Our verdict

Unproven A genuine mystery that never repeated; a natural cause is now on the table.

Sources

• Wow! signal (Wikipedia)

Checked 31 October 2026. Spotted a newer source? Tell us.