Saturday, May 21, 2022

Computer modeling explains a relativistic black hole jet

Jet from giant galaxy M87.

Messier 87 (M87) is a giant galaxy located 55 million light-years away from Earth. The galaxy has 12,000 globular clusters and a black hole called M87* with six and a half billion sun masses.

In 2019, EHT released the first picture of the black hole at the center of galaxy M87. This black hole (M87*) shoots a jet of plasma at near the speed of light. This so-called relativistic jet is originated from the gravitational pull of the black hole and requires tremendous energy to power.

Although, how a jet-like comes about and what keeps it stable across the enormous distance remains poorly understood.

To find out the answer, theoretical physicists at Goethe University and scientists from Europe, the USA, and China have modeled the center of the accretion disc surrounding M87 in great detail.

The black hole M87* pulls and swallows the matter rotating in a disc. The observation shows that this black hole jet is emitted from the center of the accretion disc surrounding M87.

Using highly sophisticated three-dimensional supercomputer simulations, they created a model in which the values calculated for the temperatures, the matter densities, and the magnetic fields correspond remarkably well with what was deduced from the astronomical observations. The model helped scientists track the complex motion of photons in the curved spacetime of the innermost region of the jet and translate this into radio images.

Scientists then compared the computer-modeled images with the observations made using numerous radio telescopes and satellites over the past three decades. The images from these calculations provide an unprecedented match with astronomical observations and confirm Einstein’s theory of general relativity.

The simulations use a huge amount of a million CPU hours per simulation. Plus, they had to simultaneously solve the equations of general relativity by Albert Einstein, the equations of electromagnetism by James Maxwell, and the equations of fluid dynamics by Leonhard Euler.

Dr. Alejandro Cruz-Osorio, a lead author of the study, comments: “Our theoretical model of the electromagnetic emission and the jet morphology of M87 matches surprisingly well with the observations in the radio, optical and infrared spectra. This tells us that the supermassive black hole M87* is probably highly rotating and that the plasma is strongly magnetized in the jet, accelerating particles out to scales of thousands of light-years.”

Professor Luciano Rezzolla, Institute for Theoretical Physics at Goethe University Frankfurt, remarks“The fact that the images we calculated are so close to the astronomical observations is another important confirmation that Einstein’s theory of general relativity is the most precise and natural explanation for the existence of supermassive black holes in the center of galaxies. While there is still room for alternative explanations, the findings of our study have made this room much smaller.”

Journal Reference:

  1. Alejandro Cruz-Osorio, Christian M. Fromm et al.: State-of-the-art energetic and morphological modeling of the launching site of the M87 jet. Nature Astronomy 2021, DOI: 10.1038/s41550-021-01506-w

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