The supermassive black hole (SMBH) located in the center of our Milky Way galaxy, Sagittarius A *, is the closest object of its kind to us, being located about 27,000 light-years from the solar system. Although it has a relatively low activity and luminosity, compared to other galactic nuclei containing SMBHs, its relatively close location leads to a higher apparent brightness compared to other similar sources, and gives astronomers a unique opportunity to study the processes occurring when the gas clouds or other space object to the edge of the black hole.
The black hole Sagittarius A * absorbs matter at a relatively low rate, amounting to several hundred Earth masses per year. However, the X-ray brightness of this source can sometimes increase hundreds of times. Most of the stable radiation is presumably associated with electrons moving along spiral trajectories at a speed close to the speed of light, along the lines of magnetic fields in a small central region with a radius of only about one astronomical unit (1 AU is equal to the average distance from the Earth to Sun), however, scientists still have not formed a consensus regarding the mechanisms of the occurrence of flares.
In the new study, a team led by R. Abuter conducted observations of the Milky Way SMBH in the X-ray (Chandra space observatory) and infrared (Spitzer space observatory) ranges. During the observation, the source Sagittarius A erupted in a powerful flash, and this allowed theorists to simulate the flash with a high level of detail for the first time.
Electrons moving in magnetic fields
Relativistic electrons moving in magnetic fields emit photons through a process known as synchrotron radiation (the most common scenario), but another process is also possible in which photons (either synchrotron radiation or other types of radiation, such as dust radiation) are scattered by electrons and thus receive additional energy, converting into X-ray photons. Modeling the combination of these effects in a small area around the Sagittarius A * source during the flare allows you to get a more detailed idea of the gas density and fields, as well as determine the flare intensity and spatial shape, and trace the course of its development.
Scientists considered several versions and came to the conclusion that the infrared flash was formed as a result of the first of the processes, and the X-ray flare was formed as a result of the second process. These conclusions allow us to draw a number of conclusions about the activity in the vicinity of SMBHs, including the conclusion that the densities of electrons and magnetic fields are comparable in magnitude with the average values, but the formation of the observed flare requires stable particle acceleration.