Wow signal! What is it and why is it still important to astronomers after 45 years?

Wow signal! Is it emitted by aliens?

After looking at a printout of encoded signals from space, a scientist with the Search for Extraterrestrial Intelligence (SETI) wrote the word “Wow!” margin of the page.

Unexpectedly, this signal has been famous for the past 45 years, serving as the basis for scientists to search for evidence of the presence of alien creatures.

The story of the Wow signal!

On a summer night in 1977, Professor Jerry Ehman of Ohio State University, USA, checked a stack of computer printouts, his usual job at SETI. It is a list of numbers and letters that are incomprehensible to the layperson.

Ehman is tasked with going through the prints to find evidence of aliens. And this time, the string of characters that appeared surprised him. Holding a red pen, he circled a series of six numbers and letters, then wrote the word “Wow!” on the sidelines, expressing surprise. What’s interesting is that from there, Wow! became a famous signal in the search for our neighbors in the universe.

But the Wow! What is it and why is it still important to astronomers after 45 years?

In the 1960s, SETI scientists wondered how a distant civilization could communicate with Earth. And radio signals come to mind.

Given the fact that the radio waves that carry music to people’s cars also travel through space, scientists speculate, it would be relatively easy for aliens to broadcast interstellar radio transmissions. To receive these signals, SETI used “Big Ear” , a giant radio telescope located in rural Ohio, USA, that continuously scanned the sky.

Until August 15, 1977, “Big Ear” received encoded signals that printed out “6EQUJ5” on a piece of paper, surrounded by the numbers 1, 2 and more.

To measure the strength of spatial transmission, SETI used the numbers 1 – 9 for weak sounds and the letter AZ for stronger sounds. The letter “A” is 10, “B” is 11… The letter “U” shown on the printout means the sound is 30 times louder than the normal disturbing sound in the space. “That’s the fun thing about ‘Wow!’” Ehman said.

Wow signal! where?

Professor Jerry Ehman and the Big Ear Radio Telescope.

Since then, 45 years have passed, the Wow! appearing only once left scientists confused. Did it come from a satellite, or from a plane crossing the sky?

Is it a military signal or a broadcast from Earth? Or is it a natural sound from a distant pulsar?

These hypotheses were quickly ruled out as inconsistent with the unique characteristics of the Wow!

Scientists say that, at Ohio State, Big Ear’s receiver monitored 50 channels – the equivalent of tuning 50 radio stations at different frequencies. But the Wow! only passes through on one channel.

Natural radio sources such as pulsars and quasars, two giant astronomical objects, emit waves that create noise across the entire spectrum so they will not produce noise on a single frequency like the Wow signal ! Furthermore, the Wow! coming on a specific frequency – the frequency of glowing interstellar hydrogen.

Hydrogen, the first element, makes up about 75% of all matter in the universe. Because it is so abundant, scientists think that an intelligent civilization might send out a signal at the frequency of hydrogen.

For the past 45 years, scientists have tried to explain this mysterious transmission. They said that the duration of the transmission – 72 seconds – seemed to come from outer space. Big Ear is fixed, relying on the Earth’s rotation to scan the sky. A transmission from distant space will gradually increase in intensity, peak and fade as the Earth rotates. That would take 72 seconds – the exact length of the Wow!

One of the biggest mysteries is why the Wow! has not been received since 1977? Why do aliens send a series of signals just once and then stop?

Scientists have hypothesized: What if aliens are also scanning the nightly sky with their beams? At this time, the Wow! will appear once, until the transmitter sweeps across the Milky Way again and intersects beams, like those of Big Ear, on Earth. However, 45 years have now passed without another transmission coming.

But in the 21st century, scientists have new tools to study space to decode the above mystery. The Very Large Array, a radio telescope in New Mexico, can receive more transmission signals than Big Ear. And the James Webb Telescope promises to capture more detailed images of outer space using infrared radiation.

In 1977, scientists did not have the technology to accurately determine the origin of the Wow! signal. At that time, Big Ear targeted a patch of space near the constellation Sagittarius, where there are millions of stars.

Today, SETI has new tools for space exploration. In addition to listening for radio signals, scientists also look for flares using “optical SETI.”

The idea is to try to detect any sudden, short, and unusually bright flashes of light, to determine whether extraterrestrials are trying to contact us by shining a space laser into the Strip. Galaxy. Will we hear the Wow signal again? According to scientists, this prospect is not far away.