NASA’s IXPE helps solve black hole jet mystery

A few of the brightest objects within the sky are known as blazars. They encompass a supermassive black hole feeding off materials swirling round it in a disk, which may create two highly effective jets perpendicular to the disk on all sides. A blazar is particularly vibrant as a result of one in every of its highly effective jets of high-speed particles factors straight at Earth. For many years, scientists have puzzled: How do particles in these jets get accelerated to such excessive energies?

NASA’s Imaging X-Ray Polarimetry Explorer, or IXPE, has helped astronomers get nearer to a solution. In a brand new examine within the journal Nature, authored by a big worldwide collaboration, astronomers discover that one of the best rationalization for the particle acceleration is a shock wave inside the jet.

“This can be a 40-year-old thriller that we have solved,” stated Yannis Liodakis, lead creator of the examine and astronomer at FINCA, the Finnish Centre for Astronomy with ESO. “We lastly had all the items of the puzzle, and the image they made was clear.”

Launched Dec. 9, 2021, the Earth-orbiting IXPE satellite, a collaboration between NASA and the Italian Area Company, supplies a particular type of knowledge that has by no means been accessible from space earlier than. This new knowledge contains the measurement of X-ray gentle’s polarization, that means IXPE detects the typical path and depth of the electrical subject of sunshine waves that make up X-rays. Details about the electrical subject orientation in X-ray gentle, and the extent of polarization, just isn’t accessible to telescopes on Earth as a result of the environment absorbs X-rays from space.

“The primary X-ray polarization measurements of this class of sources allowed, for the primary time, a direct comparability with the fashions developed from observing different frequencies of sunshine, from radio to very high-energy gamma rays,” stated Immacolata Donnarumma, the mission scientist for IXPE on the Italian Area Company. “IXPE will proceed to supply new proof as the present knowledge is analyzed and extra knowledge is acquired sooner or later.”

The brand new examine used IXPE to level at Markarian 501, a blazar within the constellation Hercules. This energetic black hole system sits on the heart of a big elliptical galaxy.

IXPE watched Markarian 501 for 3 days in early March of 2022, after which once more two weeks later. Throughout these observations, astronomers used different telescopes in space and on the bottom to assemble details about the blazar in a variety of wavelengths of sunshine together with radio, optical, and X-ray. Whereas different research have appeared on the polarization of lower-energy gentle from blazars prior to now, this was the primary time scientists may get this angle on a blazar’s X-rays, that are emitted nearer to the supply of particle acceleration.

“Including X-ray polarization to our arsenal of radio, infrared, and optical polarization is a recreation changer,” stated Alan Marscher, an astronomer at Boston College who leads the group learning big black holes with IXPE.

Scientists discovered that X-ray gentle is extra polarized than optical, which is extra polarized than radio. However the path of the polarized gentle was the identical for all of the wavelengths of sunshine noticed and was additionally aligned with the jet’s path.

After evaluating their info with theoretical fashions, the crew of astronomers realized that the info most carefully matched a situation through which a shock wave accelerates the jet particles. A shock wave is generated when one thing strikes sooner than the velocity of sound of the encircling materials, comparable to when a supersonic jet flies by in our Earth’s environment.

The examine was not designed to research the origins of shock waves, that are nonetheless mysterious. However scientists hypothesize {that a} disturbance within the stream of the jet causes a bit of it to develop into supersonic. This might end result from high-energy particle collisions inside the jet, or from abrupt strain adjustments on the jet boundary.

“Because the shock wave crosses the area, the magnetic field will get stronger, and power of particles will get larger,” Marscher stated. “The power comes from the movement power of the fabric making the shock wave.”

As particles journey outward, they emit X-rays first as a result of they’re extraordinarily energetic. Transferring farther outward, via the turbulent area farther from the situation of the shock, they begin to lose power, which causes them to emit less-energetic gentle like optical after which radio waves. That is analogous to how the stream of water turns into extra turbulent after it encounters a waterfall—however right here, magnetic fields create this turbulence.

Scientists will proceed observing the Markarian 501 blazar to see if the polarization adjustments over time. IXPE can even examine a broader assortment of blazars throughout its two-year prime mission, exploring extra longstanding mysteries in regards to the universe. “It is a part of humanity’s progress towards understanding nature and all of its exoticness,” Marscher stated.