Active galactic nuclei are powered by the supermassive black holes they contain and are the brightest objects in the universe. Light originates from jets of matter ejected at nearly the speed of light by the environment surrounding the black hole. Most often these active galactic nuclei are called quasars. But on rare occasions when one of the jets is pointing directly toward Earth, it’s called a blazer and appears brighter.
A general overview of how the blazer works has been worked out, but some details, such as how fast-moving matter produces large amounts of light, are not well understood.Now researchers are building a new space-based observatory Imaging X-ray Polarimetry Explorer (IXPE) Towards one of the brightest blazers in the sky. Data from that combined with other observations show that light is produced when a black hole jet crashes into slow-moving matter.
jet and light
IXPE specializes in detecting the polarization (the direction in which light sways in an electric field) of high-energy photons. Polarization information can tell us something about the process that created the photon. For example, photons generated in turbulent environments have an inherently random polarization, whereas more structured environments tend to produce photons with a limited range of polarizations. Light passing through matter or magnetic fields can also change its polarization.
This turned out to be useful for blazer research. The high-energy photons emitted by these objects are produced by charged particles in jets. When these objects change course or slow down, they need to release energy in the form of photons. Because they’re traveling near the speed of light, they have to give up a lot of energy, and blazers can emit across the entire spectrum, from radio waves to gamma rays. of redshift.
So the question becomes, what causes these particles to slow down? I have two main ideas. One of them is that the environment inside the jet is turbulent, with chaotic stacking of matter and magnetic fields. This slows down the particles, and the messy environment means that the polarization is highly randomized.
Another idea involves shock waves, where material from the jet collides with slower-moving material, slowing it down. This is a relatively orderly process, producing polarization that is relatively limited in extent and becomes more pronounced at higher energies.
Enter IXPE
The new series of observations is a coordinated campaign to record Blazer Markarian 501 using different telescopes that capture polarized light at longer wavelengths, with IXPE processing the highest energy photons. Additionally, the researchers searched several observatory archives to obtain previous observations of Markarian 501, allowing them to determine whether the polarization was stable over time.
Overall, the measured polarizations were within a few degrees of each other across the entire spectrum from radio waves to gamma rays. It was also stable over time and its alignment increased with higher photon energies.
There is still some variation in polarization, suggesting a relatively small disturbance at the collision site, which is not too surprising. However, it is much less chaotic than expected from turbulent materials with complex magnetic fields.
These results help us better understand how black holes produce light, but the process ultimately relies on the creation of jets that take place much closer to the black hole. . How these jets form is still poorly understood, so those studying black hole astrophysics still have reason to get back to work after a vacation weekend.
Nature2022 Doi: 10.1038/s41586-022-05338-0 (About DOIs).