Background noise from the Universe heard for the first time – rts.ch

2023-06-29 08:42:42

The background noise emitted by the whirlwind of gigantic black holes, which astronomers have been tracking for 25 years, has been identified thanks to an unprecedented technique for detecting gravitational waves. This discovery opens “a new window on the Universe”.

These results, unveiled on Thursday, are the result of a vast collaboration of the largest radio telescopes in the world. They succeeded in capturing this vibration of the Universe with “the precision of a clock”, enthuse the authors of the work published simultaneously in several scientific journals.

Predicted by Einstein in 1916 and detected a hundred years later, gravitational waves are tiny distortions of space-time, similar to ripples in water on the surface of a pond. These oscillations, which propagate at the speed of light, are born under the effect of violent cosmic events such as the collision of two black holes.

>> Read once more: Physicists have detected gravitational waves, predicted by Einstein

Even if they are linked to massive phenomena, their signal is extremely tenuous. In 2015, the gravitational wave detectors Ligo (United States) and Virgo (Europe) revolutionized astrophysics by detecting the ultra-short quiver – less than a second – of collisions between stellar black holes, of a ten times the mass of the Sun.

The “tick-tock” of the pulsars

This time, a much more time-stretched signal betrays a larger-scale phenomenon, captured by a network of radio telescopes from Europe, North America, India, Australia and China, the International Pulsar Consortium Timing Array (IPTA). A network of radio telescopes from Europe, North America, India, Australia and China have captured gravitational waves generated by black holes. [Jay Young – Green Bank Observatory via AP – Keystone]

We are talking here regarding gravitational waves generated by black holes of “several million to several billion times the mass of the Sun”, told AFP Gilles Theureau, astronomer at the Paris-PSL observatory, who coordinated the work. French side.

To detect these waves, the scientists used a novel tool: Milky Way pulsars. They were able to measure a tiny disturbance in their ticking, with “changes of less than a millionth of a second over more than 20 years”, according to Antoine Petiteau, of the Atomic Energy Commission (CEA).

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These delays were correlated, a mark of a “disturbance common to all pulsars”, according to Gilles Theureau: the characteristic signature of gravitational waves. “It was a magical moment,” said Maura McLaughlin, of the American network Pulsar Search Collaboratory.

The preferred hypothesis of the source of these waves points to pairs of supermassive black holes, each larger than our solar system, “ready to collide”, according to Gilles Theureau.

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