We finally know how black holes produce the brightest light in the universe

(ORDO NEWS) — Something that doesn’t emit light that we can detect, black holes just love to camouflage themselves in radiance.

In fact, some of the brightest light in the universe comes from supermassive black holes. Well, not actually black holes themselves; it is the material around them as they actively absorb vast amounts of matter from their immediate surroundings.

Among the brightest of these whirlpools of rotating hot material are galaxies known as blazars. Not only do they glow with the warmth of a swirling coat, but they channel the material in the form of “flaming” beams that sweep through space, emitting electromagnetic radiation with energies that are difficult to understand.

Scientists have finally figured it out. have figured out how the incredible high-energy light that reaches us billions of years ago is produced: shocks in black hole jets that accelerate particles to mind-blowing speeds.

“This is the 40th mystery that we have solved,” says astronomer Yannis Liodakis of the Finnish Center for Astronomy with ESO (FINCA). “Finally we had all the pieces of the puzzle and the picture they made was clear.”

Most galaxies in the universe are built around a supermassive black hole. These stunningly large objects are at the galactic center, sometimes doing very little (eg Sagittarius A*, the black hole at the heart of the Milky Way) and sometimes doing a lot.

This activity consists of intergrown material. A huge cloud gathers in an equatorial disk around the black hole, circling around it like water around a drain.

The interaction of friction and gravity in the extreme space surrounding a black hole causes this material to heat up and glow brightly across the wavelength range. This is one black hole light source.

The other – the one involved in blazars – is a double jet of matter emanating from the polar regions outside the black hole, perpendicular to the disk.

These jets are thought to be material from the inner edge of the disk, which, instead of falling into the black hole, is accelerated along the outer magnetic field lines to the poles, where it is ejected at very high speeds close to the speed of light.

For a galaxy to be classified as a blazar, these jets must be pointed almost directly at the observer. This is us on Earth. Due to the extreme acceleration of particles, they emit light across the entire electromagnetic spectrum, including high-energy gamma and X-rays.

How exactly this jet accelerates particles to such high speeds remains a gigantic cosmic question. decade mark.

But now, a powerful new X-ray telescope called the Imaging X-ray Polarimetry Explorer (IXPE), launched in December 2021, has given scientists a clue to the mystery. It is the first space telescope to detect the orientation or polarization of X-rays.

“The first X-ray polarization measurements of this class of sources allow for the first time a direct comparison with models developed from observations of other frequencies of light, from radio to very high energy gamma rays,” says astronomer Immacolata Donnarumma of the Italian Space Agency.

IXPE was facing the brightest high-energy object in our sky. , a blazar named Markarian 501, located 460 million light-years away in the constellation Hercules. For six days in March 2022, the telescope collected X-ray data from the blazar jet.

We finally know how black holes produce the brightest light in the universe
Illustration showing how IXPE observes Markarian 501, with the light losing energy y as it moves away from the shock front

At the same time, other observatories were measuring light in other wavelength ranges, from radio to optical, which had previously been the only available data for Markarian 501. .

The team soon noticed a curious difference in the X-ray light. Its orientation was significantly more curved or polarized than lower energy wavelengths. And optical light was more polarized than radio frequencies.

However, the direction of polarization was the same for all wavelengths and coincided with the direction of the jet.

The team found that this was consistent with models in which shocks in the jets create shock waves that provide additional acceleration along the length of the jet.

Closest to impact, this acceleration is maximized, producing X-rays. Farther down the jet, the particles lose energy, producing optical and then radio emission of lower energy with lower polarization.

“As the shock wave crosses the region, the magnetic field gets stronger and the energy of the particles gets higher,” says astronomer Alan Marcher of Boston University. “The energy comes from the energy of the movement of the material, which creates the shock wave.”

It is not clear what creates the shock wave, but one possible mechanism is that the faster material in the jet overtakes the slower clumps. leading to collisions. Future research may help confirm this hypothesis.

Since blazars are among the most powerful particle accelerators in the universe and one of the best laboratories for understanding extreme physics, this research is a pretty important piece of the puzzle.

Future studies will continue to observe Markarian 501 and look at other blazars by IXPE to see if a similar polarization can be detected.


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