Some of the brightest objects in the sky are called Blazars. It consists of a supermassive black hole feeding off material orbiting it in a disk, which can create two powerful jets perpendicular to the disk on each side. The star is particularly bright because one of its powerful jets of high-speed particles is heading straight for Earth. For decades, scientists have wondered: How are particles in these jets accelerated to such high energies?
NASA’s X-ray Imaging Explorer, or IXPE, has helped astronomers get closer to the answer. In a new study in the journal natureWritten by a major international collaboration, the astronomers found that the particle acceleration is best explained by the in-plane shock wave.
“This is a 40-year-old mystery that has been solved,” said Yannis Liudakis, lead author of the study and an astronomer at FINCA, the Finnish Center for Astronomy with ESO. “We finally got all the pieces of the puzzle in, and the picture they painted was clear.”
Launched on December 9, 2021, the Earth-orbiting satellite IXPE is a collaboration between NASA and the Italian Space Agency, and provides a special kind of data previously inaccessible from space. This new data includes X-ray photometry polarization, which means that IXPE detects the average direction and intensity of the electric field of the light waves that make up the X-rays. Information about the direction of the electric field in X-ray light, and the extent of the polarization, is not accessible to telescopes on Earth because X-rays from space are absorbed by the atmosphere.
“The first measurements of X-ray polarization for this class of sources allowed for the first time a direct comparison with models developed from observations of other frequencies of light, from radio to high-energy gamma rays,” said Immaculate Donnarumma. IXPE Project Scientist at the Italian Space Agency. “IXPE will continue to provide new evidence while analyzing existing data and acquiring additional data in the future.”
The new study used IXPE to refer to Markarian 501, which is Blazar in the constellation Hercules. This active black hole system is located at the center of a large elliptical galaxy.
I watched IXPE Markarian 501 for three days in early March 2022, and then again two weeks later. During these observations, astronomers have used other telescopes in space and on Earth to gather information about lightning in a wide range of wavelengths of light including radio, optical, and X-rays. Other studies have looked at the polarization of low-energy light from Blazars In retrospect, this was the first time scientists had been able to obtain this view of the X-rays of the blazars, which are emitted near the source of the particle acceleration.
“Adding X-ray polarization to our arsenal of radio, infrared and optical polarization is a game-changer,” said Alan Marcher, a Boston University astronomer who leads the group studying giant black holes using IXPE.
Scientists have found that X-ray light is more polarized than optical light, and it is more polarized than radio. But the direction of the polarized light was the same for all wavelengths of the observed light and it was also aligned with the direction of the jet stream.
After comparing their information with theoretical models, the team of astronomers realized that the data closely matched a scenario in which a shock wave accelerates particle jets. A shock wave is generated when something moves faster than the speed of sound of surrounding matter, such as when a supersonic jet flies through Earth’s atmosphere.
The study was not designed to investigate the origins of shock waves, which remain a mystery. But scientists hypothesize that a turbulence in the jet’s flow causes part of it to go faster than sound. This may result from collisions of high-energy particles inside the aircraft, or from sudden pressure changes at the borders of the aircraft.
As the shock wave crosses the area, the magnetic field “You get stronger, the energy of the particles increases,” Marcher said. “The energy comes from the kinetic energy of the material that’s making the shock wave.”
When the particles travel outward, they emit the X-rays first because they are so energetic. As they move farther outward, through the turbulent region away from the impact site, they begin to lose energy, emitting lower energy light as light waves and then radio waves. This is analogous to how a flow of water becomes more turbulent after it encounters a waterfall – but here, magnetic fields create the turbulence.
Scientists will continue to monitor the Markarian 501 explosion to see if its polarization changes over time. IXPE will also investigate a broader set of blazars during its two-year main mission, exploring more ancient mysteries about the universe. “It’s part of humanity’s progress toward understanding nature and all its strangeness,” Marcher said.
NASA’s Goddard Space Flight Center
the quote: NASA’s IXPE Helps Solve Mystery of Black Hole Jet (2022, November 23) Retrieved November 24, 2022 from https://phys.org/news/2022-11-nasa-ixpe-black-hole-jet.html
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