The gravitational ring of the black hole supports the theorem "no hair" – Astronomy Now

Physicists analyzing the gravity waves generated during the merging of two black holes found "harmonics" in the brief post-fusion signal, allowing them to independently calculate the resulting hole mass and rotation in accordance with the predictions of Einstein's theory of general relativity.

The analysis also confirms the "no hair" theorem, initially posited by the physicist John Archibald Wheeler, stating that the spin, mass and electric charge of a black hole are the only characteristics of the collapsed bodies that can be observed directly. .

"We all expect general relativity to be correct, but this is the first time we confirm it in this way," said Maximiliano Isi, a NASA Einstein member at the Kavli Institute for Space Research and Development. astrophysics at MIT, and lead author of the Letters of physical examination.

"This is the first experimental measurement that allows to directly test the theorem of the absence of hair. This does not mean that black holes can not have hair. This means that the image of black holes without hair is still alive one day. "

On September 9, 2015, the Observatory of Gravitational Waves by Laser Interferometer – LIGO – conducted the first observation of gravitational waves from the fusion of two black holes, an event called GW150914. The data showed a waveform that reached a net crescendo and quickly faded. Translated into sound, the researchers heard a distinctive "chirp". The strongest part of this chirp marked the moment when the two black holes collided.

The newly formed black hole probably generated its own gravitational waves during pulsations immediately after fusion, but studies have shown that the signal would be too weak to be detected with current instruments.

But earlier work led by Matthew Giesler, co-author of the new paper, showed by simulations that ephemeral harmonics should be present right after the collision. Re-analyzing the LIGO detection of GW150914, the team managed to isolate the gravitational ring from the newly formed black hole during the last few milliseconds of the chirp.

Two distinct "tones" were found, each with a tone and a drop rate that can be measured.

"We detect a global gravitational wave signal composed of several frequencies that fade at different speeds, such as the different heights constituting a sound," Isi said. "Each frequency or tone corresponds to a vibratory frequency of the new black hole."

According to the general theory or the relativity, the height and the decay of the gravitational waves of a black hole depend on its mass and its spin. The height and decay observed in signal GW150914 corresponded to measurements of black hole mass and spin determined earlier using a different technique.

"In the future, we will have better detectors on Earth and in space, and we will be able to see not only two, but dozens of modes, and precisely define their properties," said Isi. "If they are not black holes, as Einstein predicted, if they are more exotic objects such as wormholes or boson stars, they may not sound the same way and we will have a chance to see them."