Washington (AFP)
It is a paving stone, thrown into the deep sea, which creates a lot of turmoil: a respected Harvard astrophysicist claims that "Oumuamua", an interstellar object that passed close to Earth in 2017, was an extraterrestrial vehicle.
“To think that we are unique, alone and privileged is arrogant,” Avi Loeb, former director of the astronomy department at Harvard University, told AFP.
"The most sensible approach is to be modest and say: + We are not special, there are plenty of other civilizations in the universe and we just have to find them," + he insists.
The 58-year-old astrophysicist details his theory in a new book, called "Extraterrestrial. The First Sign of Intelligent Life", published at the end of January.
For this black hole specialist, conservatism and the lack of imagination of the scientific community prevent him from grasping the obvious.
- Interstellar object -
Spotted by the Pan-STARRS1 telescope in Hawaii, Oumuamua - "messenger" in Hawaiian - crossed our solar system in October 2017. Its speed was so high that it could only come from a distant star.
It is the first object detected coming from another star system.
After closer analysis of the data, researchers found that the object had thrust and deviated slightly from the path it should have followed if it was only influenced by the gravity of the Sun and the planets.
This movement could be explained in a simple way if Oumuamua had been a comet, emanating gases and debris capable of causing tiny variations in trajectory.
But such degassing was not observed.
Oumuamua also stood out for its brilliance and the great variation in its luminosity, which seemed to suggest a metallic appearance.
To explain these different anomalies, astronomers had to invent new theories.
The object could be made entirely of hydrogen ice, which would explain that a gas trail was not detected.
Another explanation: it would have disintegrated in a cloud of dust.
"These ideas devised to explain some specific characteristics of Oumuamua always involve a phenomenon that has never been observed before," says Loeb.
"So why not consider an artificial origin"?
he asserts.
- Solar sail -
There is no photo of Oumuamua.
Scientists did not learn of its existence until it was leaving our solar system.
Two shapes can correspond to the different peculiarities detected in the object: that of a cigar, long and tapered, or of a round and extremely fine pancake.
Numerical models lean towards the second and Avi Loeb is convinced that Oumuamua was conceived as a "solar sail", propelled by the radiation of the stars.
Another odd element for the American-Israeli researcher is how the object moved.
Before Oumuamua interacted with our Sun, he was in "relative stillness" to the surrounding stars, which is rare.
Rather than envisioning it as a vessel advancing in space, it should rather reverse the perspective, details Mr. Loeb.
"Oumuamua was planted like a beacon in the ocean of the cosmos and our solar system would have come close to it at high speed, like a ship in the mist," he writes in his book.
It would be for the expert, a kind of warning system, like a thread stretched by an extraterrestrial civilization, waiting to be triggered.
- Archeology of space -
Avi Loeb's unorthodox theses have been heavily criticized by the scientific community.
"Rather than respond to their scientific objections, he has completely stopped listening to other astronomers", preferring that the general public be the judge of his theory, denounced the American astrophysicist Ethan Siegel in the journal Forbes.
M. Loeb, who evokes Galileo many times in his book, a scientist imprisoned in the 17th century for having asserted that the Earth revolved around the Sun, criticizes for his part an academic "culture of intimidation".
Finding signs of extraterrestrial life is more common sense than studying dark matter or multiple universes, he says.
He thus hopes for the creation of a new branch of astronomy, archeology of space, dedicated to the quest for biological and technological traces of extraterrestrial civilizations.
“If we find evidence of technologies that took millions of years to develop, then we can find a shortcut to (them), and use them on Earth,” Avi Loeb hopefully notes.
© 2021 AFP