Deutsch Intern

    New Computer Model for Black Holes


    The black hole of the giant galaxy M87 shoots out an enormous jet of particles. A theoretical model of this jet has now been developed that fits astronomical observations very well.

    The theoretical model (left) and the astronomical observations of the launching site of the relativistic jet of M87 are a very good match.
    The theoretical model (left) and the astronomical observations of the launching site of the relativistic jet of M87 are a very good match. (Image: Alejandro Cruz-Osorio / Goethe Universität Frankfurt)

    The galaxy Messier 87 (M87) is located 55 million light years away from Earth in the Virgo constellation. It is a giant galaxy with 12,000 globular clusters, making the Milky Way’s 200 globular clusters appear modest in comparison.

    A black hole of six and a half billion sun masses is harboured at the centre of M87. It is the first black hole for which an image exists, created in 2019 by the international research collaboration Event Horizon Telescope.

    This black hole shoots a jet of plasma at near the speed of light, a so-called relativistic jet, on a scale of 6,000 light years. The tremendous energy needed to power this jet probably originates from the gravitational pull of the black hole, but how a jet like this comes about and what keeps it stable across the enormous distance is not yet fully understood.

    Three-dimensional supercomputer simulations

    The black hole of the galaxy M87 attracts matter that rotates in a disc in ever smaller orbits until it is swallowed by the black hole. The jet is launched from the centre of this disc surrounding M87.

    Theoretical physicists at Goethe University Frankfurt together with scientists from the Harvard University, Julius-Maximilians-Universität Würzburg (JMU), University of Shanghai, the University College London, the University of Amsterdam, the Radboud University Nijmegen, and the Max Planck Institute for Radio Astronomy in Bonn, have now modelled this region in great detail.

    They used highly sophisticated three-dimensional supercomputer simulations that use the staggering amount of a million CPU hours per simulation and 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.

    Model corresponds remarkably well with observations

    The result was a model in which the values calculated for the temperatures, the matter densities and the magnetic fields correspond remarkably well with what deduced from the astronomical observations.

    On this basis, scientists were able to track the complex motion of photons in the curved spacetime of the innermost region of the jet and translate this into radio images. They were then able to compare these computer modelled images with the observations made using numerous radio telescopes and satellites over the past three decades.

    Dr Alejandro Cruz-Osorio, lead author of the study, comments: “Our theoretical model of the electromagnetic emission and of the jet morphology of M87 matches surprisingly well with the observations in the radio, optical and near-infrared regime. This tells us that the supermassive black hole of 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 centre of galaxies. While there is still room for alternative explanations, the findings of our study have made this room much smaller.”

    Dr Christian M. Fromm, who moved from Harvard University to the JMU Chair of Astronomy as head of a junior research group at the beginning of October 2021, was also involved in the study: “In the coming years we will further investigate the formation of jets and the underlying particle acceleration mechanisms throughout the entire electromagnetic spectrum using modern computer simulations and state-of-the art observations within the newly founded DFG Research Unit on Relativistic Jets at the Julius Maximilians University Wuerzburg and partner institutes in Germany and abroad”.


    Alejandro Cruz-Osorio, Christian M. Fromm, Yosuke Mizuno, Antonios Nathanail, Ziri Younsi, Oliver Porth, Jordy Davelaar, Heino Falcke, Michael Kramer, Luciano Rezzolla: State-of-the-art energetic and morphological modelling of the launching site of the M87 jet. Nature Astronomy 2021, https://doi.org10.1038/s41550-021-01506-w

    Contact person at JMU

    Dr. Christian M. Fromm, Chair of Astronomy, JMU Wuerzburg, christian.fromm@uni-wuerzburg.de

    Additional images

    By Robert Emmerich