Traditional sci-fi makes it appear to be our first contact with aliens shall be completely unmistakeable: a large, unearthly spaceship touchdown on Earth with creatures that come out to greet us, or a message that someway we are able to readily and confidently translate. However in actuality, the seek for extraterrestrial intelligence (referred to as SETI) is rather a lot more durable.
[ Related: How scientists decide if they’ve actually found signals of alien life ]
In 1977, Ohio State’s Huge Ear telescope was listening for alerts from clever life past Earth—and far to everybody’s shock, they recorded a transmission that appeared prefer it may really be the true deal. Astronomer Jerry R. Ehman was so stunned, in actual fact, that he wrote “Wow!” on the printed out information whereas reviewing it, giving this sign its identify.
“The Wow! sign is fascinating to me as a result of—as of now—nothing has ever come near explaining it. It’s precisely the frequency you’d select if you happen to had been attempting to ship a radio wave a really lengthy methods via area,” explains Seven Rasmussen, astronomer and creator of the upcoming astrobiology guide Life in Seven Numbers. “Personally, it’s my all-time favourite doable technosignature,” they add. Nonetheless, the Wow! sign has but to be detected once more, leaving astronomers questioning what prompted this bizarre statement.
Lots of issues in area really emit radio waves, and astronomers use all wavelengths of sunshine (radio very a lot included!) to check the cosmos. For instance, radio waves enabled the well-known first-ever picture of a black gap from a couple of years again. Additionally they helped Jocelyn Bell Burnell uncover a wierd kind of useless star referred to as a pulsar, and revealed disks of gasoline that function nurseries for planets round different stars.
All these pure sources have one thing in frequent: they emit a reasonably broad vary of radio frequencies. One form of technosignature—an indication of expertise, or equivalently, clever life past Earth—is a so-called narrowband radio sign. Whereas nature largely produces broadband alerts, expertise can create very centered messages.
“To have a very convincing technosignature, you want one thing which has unquestionably been created with intent. The intent may very well be a instrument, or a habitat, or a message, or a murals. However we must be sure that it couldn’t happen naturally,” says Rasmussen. “Nature can create proper angles (pyrite, bismuth, all method of crystals), however not, say, a home.”
Scientists additionally take into account a wide range of technosignatures apart from radio pictures, from the sci-fi idea of a Dyson sphere harnessing an entire star’s power to extra relatable technological results like air pollution in a planet’s ambiance. However the concept of listening to a radio sign from aliens has actually caught in our minds, immortalized in the film Contact the place Jodie Foster listens to a radio telescope with old-school headphones. (It’s value noting that, sadly, actual radio telescopes don’t usually work like that–there’s no lightning port to plug in your earbuds.)
Some astronomers are nonetheless looking for radio technosignatures (together with a repeat of the Wow! sign from the path of the constellation Sagittarius) equivalent to with the Breakthrough Pay attention mission, utilizing radio telescopes just like the Allen Telescope Array in California or the Inexperienced Financial institution Telescope in West Virginia. But none of those surveys have but to seek out something extra convincing than the Wow! sign, which was each narrowband and at an attention-grabbing, presumably specially-chosen wavelength: 21 centimeters, an essential wavelength for one of many traces of atomic hydrogen, essentially the most ample part of the universe.
On the similar time, different astronomers are working to clarify the Wow! sign with pure astrophysics. In a just lately posted preprint, a world group of astronomers trawled via information archives from Puerto Rico’s Arecibo Observatory, as soon as the most important single dish telescope on the earth earlier than its catastrophic collapse in 2020. They discovered some alerts just like Wow!, however may simply attribute them to clouds of chilly hydrogen floating round between stars. In consequence, they recommend that the Wow! sign was maybe an astronomical maser flare, a sudden brightening of a type of clouds as a consequence of some close by cosmic explosion. Rasmussen describes this as “essentially the most compelling speculation I’ve heard, however I’d like to seek out the magnetar/SGR chargeable for the maser earlier than I say it was positively a pure phenomenon.”
As radio SETI searches develop, maybe we’ll discover extra of those maser flares or different doable messages from past—or possibly, even a repeat of the famed Wow! sign itself.