June 29, 2023

2023-06-29 11:46:37
The background noise emitted by the whirlwind of black holes is heard for the first time The background noise emitted from the whirlwind of giant black holes, following astronomers sought for a quarter of a century to track it, has finally been detected. What made it possible to hear them for the first time was an unprecedented technique for detecting gravitational waves, which opens a “new window on the universe.” These results, which were announced today, Thursday, are the result of a large-scale collaboration of the largest radio telescopes in the world that were able to capture this vibration of the universe “with clock accuracy”, which excited the authors of the study published simultaneously in more than one scientific journal. Gravitational waves, the existence of which Einstein was the first to point out in 1916, and were actually observed a hundred years later, are tiny distortions in space-time, like ripples in water on the surface of a pond. These oscillations, which propagate at the speed of light, are caused by violent cosmic events, such as the collision of two black holes. It is noteworthy that its signals are very weak, although they are caused by huge phenomena. In 2015, the gravitational-wave detectors LIGO (USA) and Virgo (Europe) revolutionized astrophysics by detecting the sub-second tremor caused by collisions between 10 times the mass of stellar black holes. the sun. This time, a signal that lasts for a much longer time shows a large-scale phenomenon that was monitored by a network of radio telescopes (from Europe, North America, India, Australia and China), of the International Federation, for the timing of pulsars. The astronomer at the Paris-BSL Observatory, Gilles Toro, who coordinated the work of the French side, explained that the matter is related to gravitational waves generated by black holes, which “are millions to billions of times greater than the size of the sun’s mass.” To detect these waves, scientists used a new tool: pulsars from the Milky Way. These stars are characterized by the fact that their mass is equivalent to between one and two suns, compressed into a ball with a diameter of regarding ten kilometers. These very small stars revolve around themselves at a high speed of up to 700 revolutions per second, according to the researcher at the French National Center for Scientific Research. This high-speed rotation produces magnetic radiation at the poles, similar to the rays of a beacon, that can be detected thanks to radio waves emitted from low frequencies. At each rotation, the pulsars send out highly regular “beeps”, which makes them “amazing natural clocks”, explains Luca Guimeau of the Laboratory of Physics and Chemistry for the Environment and Space (LPC2E) in Orleans, France. Scientists made a list of groups of pulsars through which they reached a “celestial web” in the zigzags of space-time, and were able to measure a slight disturbance in the “ticking” of these stars, with “changes of less than a millionth of a second over more than 20 years,” according to him. by Antoine Potito, from the Atomic Energy Authority. It turns out that these delays are interconnected, a sign of “a disturbance common to all pulsars”, according to Gil Toro, which characterizes gravitational waves. “It was a magical moment,” said Maura McLaughlin, of the American Pulsar Search Collaborator, during a press conference. As in a noisy restaurant, what is the source of these waves? The most likely hypothesis refers to pairs of supermassive black holes, each larger than our solar system, “ready to collide,” explains Gilles Toro. Antoine Potito likened it to two giants “turning around before merging”, a dance that causes gravitational waves of “months to years” duration. Michael Keith, of the European Pulsar Timing Matrix, compared this constant background noise to “a noisy restaurant with loads of people talking”. The measurements do not yet allow us to determine whether this noise indicates the presence of a few pairs of black holes, or the presence of a large group. Another hypothesis refers to the existence of a source in the very early ages of the universe, during which it witnessed what is called an inflationary stage. Gil Toro considered that this discovery opens a “new window on the universe,” and said, “We are adding a new set of information sources,” complementing the research of “Ligo” and “Virgo” and working on different wavelengths, according to Antoine Potito, which can explain The mystery of the formation of massive black holes. However, in-depth studies, expected to be carried out within a year, must be carried out to enhance the strength of the discovery, and to ensure that this matter is “not a coincidence,” according to what the Paris Observatory, the National Center for Scientific Research, the Atomic Energy Authority, and the Universities of Orleans and Paris City confirmed in a statement. (AFP)
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