2023-07-05 05:30:20
— © Aurore Simonnet for the NANOGrav Collaboration
After years of searching, researchers have finally managed to capture the whispers of the Universe: a steady stream of low-frequency ripples in spacetime.
Cosmic background noise
THE gravitational waves are distortions of spacetime itself, first predicted by Albert Einstein over a century ago. But it was not until 2015 that they might be captured directly thanks to the LIGO installation. Since then, a hundred detections have been made.
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If these were always high-frequency signals, coming from the collisions of dense objects such as black holes and neutron stars, it had long been predicted the existence of a kind of background noise, consisting of signals of much lower frequency propagating slowly in theUniverse.
While previous observations had been made using underground facilities emitting lasers into long tunnels and looking for tiny distortions of light indicating the passage of a gravitational wave, the new approach, detailed in The Astrophysical Journalinvolved a galactic network of 68 pulsars milliseconds.
— posteriori / Shutterstock.com
A great first
Compared to cosmic atomic clocks, these remnants of rapidly rotating collapsed stars emit electromagnetic pulses at extremely regular intervals, a significant shift in which may reveal the passage of very low frequency gravitational waves. The careful examination of the data collected over 15 years within the framework of the NANOGrav project has made it possible to detect for the first time these ” whispers ».
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« We had to take into account a multitude of puzzling effects, such as the movement of pulsars, disturbances due to free electrons in our galaxy, instabilities in the reference clocks of radio observatories, and even the precise location of the center of the Solar system, which we determined with the help of NASA’s Juno and Cassini missions “, underlines the physicist Michele Vallisneri.
It is believed that this background noise results from phenomena much larger than those at the origin of the signals picked up by LIGO. Potentially mergers of supermassive black holeswhose mass turns out to be millions of times greater than that of their “classic” counterparts and neutron stars. According to the team, the detections will become increasingly precise as more telescopes join the project.
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