Black holes: their high-energy radiation strikes Earth as well

Stand: 4:46 PM.| Reading time: 3 minutes

IIn April 2019, the first “image” of a supermassive black hole made headlines. Image captured with the Event Horizon Telescope (EHT) – a global network of telescopes operating in the radio wave range.

A black hole containing 6.6 billion solar masses at the center of the distant galaxy M87, 55 million light-years away, cannot be visible of course – but the glowing ring of hot matter that surrounds the black hole. It is the origin of radio waves captured by telescopes. Then a black circular area remains in the center.

Since then, researchers have discovered the M87 black hole not only with EHT, but also with other telescopes that can record electromagnetic radiation in other wavelength ranges. Infrared and visible light were measured, as well as x-rays and gamma rays.

Simultaneous multi-spectral black hole measurements of M87 are now presented in “Astrophysical Journal Letters.” 760 scientists and engineers participated in 19 observatories and about 200 research institutes. Never before has a black hole been discovered with such a broad scale. “This is a great example of how astronomers around the world can collaborate in the service of science,” says co-author Juan Carlos Alpa. University of Malaya In Kuala Lumpur.

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Scientists hope the measurement data will provide a better understanding of processes occurring near a black hole. Matter in cosmic proximity is attracted by its gigantic gravity. It collects into a disk that rapidly rotates around the black hole and heats up to very high temperatures in the process. Because the material in the so-called collecting disk is very hot, it emits radiation in nearly all regions of the electromagnetic spectrum.

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Some of this material is swallowed up by the black hole. Another portion is ejected into space from the rotating disk as an intensely focused ray of matter at nearly the speed of light. These so-called jets get their energy from the strong magnetic fields around the black hole. However, the details of this process are not yet well understood. Jet particles are so energetic that they are leaving the galaxy.

Researchers believe that it is possible that some so-called cosmic rays, which constantly hit the Earth, originate in such jets from a black hole. Some particles in cosmic rays have millions of times more energy than protons at the world’s largest particle accelerator. LHC At the Geneva Research Center CERN It is speeded up.

So far, there is no other explanation for the extremely high energy of cosmic rays other than acceleration near a black hole. The measurement data can help to better understand the mechanism of jet formation and to determine the exact location in which the particle acceleration occurs.

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“Understanding this acceleration goes hand in hand with understanding black hole images in all its different colors, ie wavelengths,” says EHT astronomer Sira Markov of University of Amsterdam“The results of the measurements will help us calculate the amount of energy transmitted and the effect of the black hole jets on their surroundings.”

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Stephanie Comosa from Max Planck Institute for Radio Astronomy In Bonn, who has also participated in the EHT measurements, he adds: “This unique data set is essential for our understanding of physical conditions in the immediate vicinity of one of the largest black holes in our cosmic neighborhood.”

On the basis of the measurement data, the researchers want to pursue another fundamental question: “Are the observations consistent with Albert Einstein’s general theory of relativity? Even the slightest deviations will reveal themselves in this data. The measurements are, as they were, a very accurate test of the validity of Einstein’s theory.