The Wow! Signal: A Possible Alien Radio Message That Remains Unexplained

On August 15, 1977, a mysterious 72-second radio signal was detected from deep space—one so unusual that astronomer Dr. Jerry Ehman circled it on the data printout and wrote a single word beside it: “Wow!”

Known today as the Wow! Signal, this unexplained radio burst remains one of the strongest candidates for an extraterrestrial communication attempt. Despite decades of investigation, no natural or human-made source has been identified. Could this be proof of intelligent alien life, or is there another explanation?

Discovery of the Wow! Signal

The signal was detected at the Big Ear Radio Observatory in Ohio, which was part of the Search for Extraterrestrial Intelligence (SETI) program.

???? Duration: 72 seconds
???? Frequency: 1420.456 MHz (close to the frequency of neutral hydrogen, a key cosmic element)
???? Location: Appeared to come from the constellation Sagittarius, near the star cluster M55
???? Uniqueness: The signal was extremely strong and clear, unlike typical space noise

Dr. Ehman’s handwritten “Wow!” perfectly captured the excitement of this unexpected discovery.

What Made the Wow! Signal Special?

Several factors make the Wow! Signal extraordinary and different from other radio signals:

✔ It matched SETI's expectations for an artificial alien transmission. Scientists expected that an intelligent civilization might use the 1420 MHz hydrogen frequency to send signals, as hydrogen is the most abundant element in the universe.
✔ It was extremely strong but only lasted for one observation period—meaning it wasn’t a continuous transmission.
✔ It never repeated. Despite multiple follow-up attempts over the years, the signal was never detected again.

Possible Explanations for the Wow! Signal

Although some believe the Wow! Signal could have been an extraterrestrial message, scientists have proposed alternative explanations.

1. A Transmission from an Alien Civilization ????

SETI researchers consider the Wow! Signal one of the best candidates for an intelligent alien broadcast. Its strength, frequency, and lack of known earthly sources make it an exciting possibility. However, without a repeat signal, it’s impossible to confirm.

2. A Natural Cosmic Phenomenon ????

Some scientists suggest that the signal may have been caused by a natural space event, such as:

• A rare cosmic radio burst
• A reflection of a stellar object
• An unknown interstellar signal source

However, no known astronomical phenomenon fully explains the signal's characteristics.

3. A Signal from a Passing Comet ☄

In 2017, a new theory emerged suggesting that the Wow! Signal could have come from a hydrogen cloud surrounding a comet, specifically Comet 266P/Christensen or Comet 335P/Gibbs. But this theory remains controversial and has not been widely accepted.

4. A Signal from a Secret Human Source ????

Some believe the signal might have been caused by an unknown human-made transmission, such as:

• A military satellite
• An experimental radio burst from Earth

However, no known human signal matched its characteristics, and the direction of the signal came from deep space, making an Earth-based source unlikely.

Why Haven’t We Heard It Again?

The biggest challenge with the Wow! Signal is that it never repeated. Scientists have searched the same region of space multiple times using advanced radio telescopes, but nothing similar has ever been detected.

This raises key questions:

• Was the signal a one-time transmission from an alien civilization?
• Did we catch only part of a longer message?
• Did the source stop transmitting, or was it moving?

The Wow! Signal’s Legacy

Although the Wow! Signal remains unexplained, it has inspired generations of scientists and space enthusiasts. It proves that mysterious, unexplained signals exist in space and reminds us that the search for extraterrestrial life is still ongoing.

With modern telescopes and improved technology, SETI continues to scan the skies for another “Wow!” moment. Will we one day receive a second signal that confirms we are not alone?