In 2008, humanity attempted something crazy: sending a message to an exoplanet located at 21 light years, in the hope, as thin as it is, that an intelligent life form captures it, understands it and … responds.
The planet in question is called Gliese 581c. It revolves around a red dwarf star named Gliese 581, located in the constellation of the scale. Discovered a year earlier, in 2007, this planet had briefly attracted the attention of the scientific community because of its proximity to what is called the “habitable zone”: a region around a star where liquid water – and therefore potentially life – could exist.
A super-terre that makes you dream
Gliese 581C belongs to the category of “super-terres”. It is approximately 5.5 times more massive than the earth, and although it is considered today to be probably too hot to shelter liquid water, its theoretical potential of habitability has not been completely dismissed.
In reality, the first models of the time placed Gliese 581c just inside or just outside of the internal limit of the habitable area, according to the hypotheses selected (type of atmosphere, cloud cover, greenhouse effects, etc.). In summary, it is highly improbable that the planet is home to life as we know it, but not strictly impossible.
A message from Bebo
This did not prevent a daring – and a little eccentric project – from seeing the light of day. In October 2008, as part of the “Message from Earth” project, a radio signal was sent from Ukraine to Gliese 581c.
Unlike the formal messages of traveling probes, carefully drawn up under the supervision of scientists like Carl Sagan, the content of this interstellar message has been largely shaped by users of the Bebo social network, now disappeared. More than 500 messages, images and texts have been selected by Internet users, with contributions from deep to the frankly Sagrenu.
Among the elements sent: photos of Hillary Clinton, of British TV presenters, a montage of Barack Obama and George W. Bush (symbolizing good and evil, according to Gillian Anderson, actress of X-Files), an image of Cheryl Cole designated as representing the “perfect body”, as well as messages on peace or the sense of life.
Gliese 581 photographed by the Sloan Digital Sky Survey. Image credit: Sloan Digital Sky Survey via ESO
A 42 year old round trip
The signal will take 21 years to reach its target. He will therefore arrive at destination in 2029. In the highly speculative hypothesis where an extraterrestrial civilization would exist on this planet, that it has radio technologies, that it captures the message, understands it and responds immediately, the answer would not arrive on Earth until 2050.
This scenario is, of course, extremely improbable. The planet has not yet revealed any signs of confirmed habitability, and the probability that intelligent beings are there, ready to interact, remains tiny. And yet, this project raises a dizzying question: what would we choose to send in space if we had the opportunity to represent humanity to unknown beings?
A cosmic joke?
It is fascinating-and perhaps a little embarrassing-to think that our interstellar business card could include celebrities, ephemeral cultural memes and subjective beauty choices, rather than carefully elaborate scientific, humanist or philosophical messages.
But this project also reveals something deeply human: our need to tell, to reach out, to look for an echo in the universe, even when the chances are close to zero. The idea of not being alone has fueled our imagination for centuries. Sending a message to an exoplanet is perhaps less a scientific act than a symbolic, poetic gesture, a mirror of our time and its obsessions.
A tenacious hope
Since 2008, studies have refined our understanding of the Gliese 581 system. Some of them cautiously re -evaluate the habitability of certain planets of the system, including Gliese 581c. Scenarios involving extreme forms of life – capable of surviving in extreme conditions – have also been proposed.
However, this remains pure speculation. But in science, speculation is sometimes the starting point for unexpected advances. And even if Gliese 581c turns out to be sterile, the simple fact that humanity has turned to it says a lot about our curiosity without borders – and our ability to dream very, very far.