Astrophysicists solve mystery of 40-year-old black hole jet with NASA’s IXPE

This illustration shows NASA’s IXPE spacecraft, at right, observing the blazar Markarian 501, at left. A blazar is a black hole surrounded by a disk of gas and dust with a bright jet of high-energy particles aimed at Earth. The inset illustration shows high-energy particles in the jet (blue). Credit: NASA/Pablo García

Blazars are some of the brightest objects in the cosmos. They are composed of a supermassive

“This is a 40-year-old mystery that we have solved,” said Yannis Liodakis, lead author of the study and an astronomer at FINCA, the Finnish Center for Astronomy with IXPE in Earth orbit

Artist’s impression of IXPE in Earth orbit. Credit: NASA

Launched on December 9, 2021, the IXPE satellite into Earth orbit, a collaboration between

“This is a 40-year-old mystery that we have solved. In the end we had all the pieces of the puzzle and the picture they had created was clear.” — Yannis Liodakis

“The first X-ray polarization measurements of this class of sources allowed, for the first time, a direct comparison with models developed from the observation of other frequencies of light, from radio rays to very high-energy gamma rays,” he said. affirmed Immacolata Donnarumma, project scientist for IXPE at the Italian Space Agency. “IXPE will continue to provide new evidence as current data is analyzed and more data is acquired in the future.”

The new study used IXPE to indicate Markarian 501, a blazar located about 450 million light-years from Earth in the constellation Hercules. This active black hole system is located at the center of a large elliptical galaxy.

IXPE watched Markarian 501 for three days in early March 2022, and then again two weeks later. During these observations, astronomers used other telescopes in space and on the ground to gather information about the blazar in a wide range of wavelengths of light, including radio, optical and X-rays. While other studies have looked at the polarization of light low-energy from blazars in the past, this was the first time scientists have been able to gain this perspective on a blazar’s X-rays, which are emitted closest to the source of the particle’s acceleration.

NASA's IXPE helps solve mystery of black hole jet

This illustration shows NASA’s IXPE spacecraft, at right, observing the blazar Markarian 501, at left. A blazar is a black hole surrounded by a disk of gas and dust with a bright jet of high-energy particles aimed at Earth. The inset illustration shows high-energy particles in the jet (blue). When particles hit the shock wave, depicted as a white bar, the particles become excited and emit X-rays as they accelerate. As they move away from the shock, they emit low-energy light: first visible, then infrared and radio waves. Further away from the shock, the magnetic field lines are more chaotic, causing more turbulence in the particle stream. Credit: NASA/Pablo García

“Adding X-ray polarization to our arsenal of radio, infrared and optical polarization is a game changer,” said Alan Marscher, a Boston University astronomer who leads the team studying giant black holes with IXPE.

Scientists have discovered that X-ray light is more polarized than optical light, which is more polarized than radio. But the direction of the polarized light was the same for all wavelengths of light observed and was also aligned with the direction of the jet.

After comparing their information with theoretical models, the team of astronomers realized that the data most closely matched a scenario in which a shock wave accelerates jet particles. A shock wave is generated when something moves faster than the speed of sound of the surrounding material, such as when a supersonic jet flies through the Earth’s atmosphere.

The study wasn’t designed to investigate the origins of shock waves, which are still mysterious. But scientists speculate that a disturbance in the jet’s flow causes parts of it to go supersonic. This could result from collisions of high-energy particles within the jet or from abrupt pressure changes at the jet boundary.

“As the shock wave travels through the region, the magnetic field gets stronger and the energy of the particles increases,” Marscher said. “The energy comes from the energy of motion of the material that creates the shock wave.”

As the particles travel outward, they first emit X-rays because they are extremely energetic. Moving further outward, through the turbulent region farther from the shock location, they begin to lose energy, which causes them to emit less energetic light as optical waves and then radio waves. This is analogous to how the flow of water becomes more turbulent after encountering a waterfall, but here the magnetic fields create this turbulence.

Scientists will continue to observe blazar Markarian 501 to see if the polarization changes over time. IXPE will also investigate a larger collection of blazars during its first two-year mission, exploring long-held mysteries about the universe. “It’s part of humanity’s progress toward understanding nature and all its exoticness,” Marscher said.

Reference: “Blazar polarized X-rays imply acceleration of particles in collisions” by Ioannis Liodakis, Alan P. Marscher, Iván Agudo, Andrei V. Berdyugin, Maria I. Bernardos, Giacomo Bonnoli, George A. Borman, Carolina Casadio, Vi´ctor Casanova, Elisabetta Cavazzuti, Nicole Rodriguez Cavero, Laura Di Gesu, Niccoló Di Lalla, Immacolata Donnarumma, Steven R. Ehlert, Manel Errando, Juan Escudero, Maya Garci’a-Comas, Beatriz Agi’s-González, César Husillos, Jenni Jormanainen, Svetlana G. Jorstad, Masato Kagitani, Evgenia N. Kopatskaya, Vadim Kravtsov, Henric Krawczynski, Elina Lindfors, Elena G. Larionova, Grzegorz M. Madejski, Frédéric Marin, Alessandro Marchini, Herman L. Marshall, Daria A. Morozova, Francesco Massaro, Joseph R. Masiero, Dimitri Mawet, Riccardo Middei, Maxwell A. Millar-Blanchaer, Ioannis Myserlis, Michela Negro, Kari Nilsson, Stephen L. O’Dell, Nicola Omodei, Luigi Pacciani, Alessandro Paggi, Georgia V. Panopoulou , Abel L Peirson, Matteo Perri, Pierre-Oli vier Petrucci, Juri Pou tanen, Simonetta Puccetti, Roger W. Romani, Takeshi Sakanoi, Sergey S. Savchenko, Alfredo Sota, Fabrizio Tavecchio, Samaporn Tinyanont, Andrey A. Vasilyev, Zachary R. Weaver, Alexey V. Zhovtan, Lucio A. Antonelli, Matteo Bachetti, Luca Baldini, Wayne H. Baumgartner, Ronaldo Bellazzini, Stefano Bianchi, Stephen D. Bongiorno, Raffaella Bonino, Alessandro Brez, Niccoló Bucciantini, Fiamma Capitanio, Simone Castellano, Stefano Ciprini, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, Alessandro Di Marco, Victor Doroshenko, Michal Dovciak, Teruaki Enoto, Yuri Evangelista, Sergio Fabiani, Riccardo Ferrazzoli, Javier A. Garcia, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, Wataru Iwakiri, Vladimir Karas, Takao Kitaguchi, Jeffery J Kolodziejczak, Fabio La Monaca, Luca Latronico, Simone Maldera, Alberto Manfreda, Andrea Marinucci, Giorgio Matt, Ikuyuki Mitsuishi, Tsunefumi Mizuno, Fabio Muleri, Stephen C.-Y. Ng, Chiara Oppedisano, Alessandro Papitto, George G. Pavlov, Melissa Pesce-Rollins, Maura Pilia, Andrea Possenti, Brian D. Ramsey, John Rankin, Ajay Ratheesh, Carmelo Sgro, Patrick Slane, Paolo Soffitta, Gloria Spandre, Toru Tamagawa, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicolas E. Thomas, Francesco Tombesi, Alessio Trois, Sergey Tsygankov, Roberto Turolla, Jacco Vink, Martin C. Weisskopf, Kinwah Wu, Fei Xie and Silvia Zane, November 23, 2022, Nature.
DOI: 10.1038/s41586-022-05338-0

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