An international team of astronomers used the horizon telescope to measure the characteristics of the magnetic field around a black hole, called polarization. Polarization is the direction of electric field in light and radio waves, which can indicate the existence and arrangement of magnetic field. The event horizon telescope is composed of eight radio telescopes, including the large millimeter wave/submillimeter wave array (ALMA) in Atacama, Chile.
Monica, coordinator of EHT polarization measurement working group and associate professor of Radburg University in the Netherlands? Cibrodzka said: "We now see the next key evidence to understand how the magnetic field around the black hole behaves and how activities in this very compact space region drive powerful jets."
The new images taken by EHT and Alma enable scientists to draw magnetic field lines near the edge of M87 black hole. This black hole was also imaged for the first time in history-photographed by EHT at 20 19. This picture shows a bright ring structure with a dark area in the middle-the shadow of a black hole. The latest image is the key to explain how M87, 50 million light-years away from the Earth, emits high-energy jets from its core.
The mass of the black hole at the center of M87 is more than 6 billion times that of the sun. The sucked matter forms a rotating disk-called an accretion disk-which closely orbits the black hole. Most of the material in the disk falls into the black hole, but some particles around it escape and are ejected into space at a speed close to the speed of light. Andrew Chael, a NASA Hubble researcher at the Princeton Center for Theoretical Science and the Princeton Gravity Project, said: "The newly published polarized image is the key to understanding how magnetic fields make black holes' swallow' matter and emit powerful jets."
Scientists have compared the new images showing the external magnetic field structure of black holes with computer simulations based on different theoretical models. They found that only the model characterized by strongly magnetized gas can explain what they saw in the horizon telescope.
"The observation results show that the magnetic field at the edge of the black hole is strong enough to push back the hot gas and help it overcome gravity." Jason Dexter, an associate professor at the University of Colorado at Boulder and coordinator of the EHT Theory Working Group, explained: "Only the gas that slips through the magnetic field can rotate inward to the event horizon."
In order to make new observations, scientists connected eight telescopes around the world-including ALMA-to create a virtual earth-sized telescope, namely EHT. The plan improves the angular resolution of the telescope to a level sufficient to observe the scale structure of the event horizon. This resolution enables the research team to directly observe the shadow of the black hole and the halo around it, and the new image clearly shows that the halo is magnetized. These results were published in two papers in the Journal of Astrophysics, which was co-sponsored by EHT. The study involved more than 300 researchers from many organizations and universities around the world.
The third paper was also published in the same volume of Astrophysics Journal Express, based on the data of ALMA, and was led by Ciriaco Goddi, a scientist from Ladeburg University in the Netherlands and Leiden Observatory. Gordy said: "The comprehensive information from EHT and Alma enables scientists to study the role of the magnetic field from near the event horizon to outside the core of the galaxy, extending thousands of light-years along its powerful jet."