Three years ago we saw for the first time the supermassive black hole that inhabits the center of our galaxy. Now the James Webb space telescope has opened a window to study its surroundings. And it has turned out to be a chaotic show of lights that never stops.
Context. In the center of the Milky Way inhabits a gigantic black hole called Sagittarius A*. Astronomers have managed to unravel the extreme dynamics of their accretion disk, the spiral of gas and dust that turns around it. To do this, they observed it for 48 hours (distributed in several periods of 2023 and 2024) using the Nircam instrument of the Webb Telescope.
A disco ball. The observations revealed that SGR A* issues a continuous game of lights and flashes that is characterized by constant blinking interspersed with a series of intense eruptions.
These emissions have a weak and continuous component, probably originated in the internal turbulence of the disc, and a bright and short -term component, eruptions associated with magnetic reconnection, in which magnetic fields collide and release huge amounts of energy. Fluctuations can occur in seconds or as changes that extend for days, weeks and months.
The explanation. The study of these variable emissions, published in The Astrophysical Journal Letters, suggests that fluctuations intensify at major scales. According to researchers, the small internal disturbances of the disk, associated with fluctuations in density and magnetic field, generate the faint flashes, while large eruptions are related to specific events of magnetic reconnection, comparable to the solar flares, but at levels much older energy.
“In our data we observe a luminosity in constant change,” explains Farhad Yusef-Zadeh, main author of the study. “Suddenly, boom!, A great explosion of brightness appears suddenly and then calms down, without following a fixed pattern.” This, apparently random nature, demonstrates that the accretion album is regenerated all the time, causing between five and six great daily rashes, in addition to multiple intermittent outbreaks.
The lags. An advantage of the NIRCAM instrument of the Webb Telescope is its ability to observe two infrared wavelengths simultaneously (2.1 and 4.8 micrometers). This allowed researchers to compare how the brightness of eruptions with each wavelength changed.
Surprisingly, they discovered that the events observed in the shortest wavelength changed shine a little before the events of the longest. “It is the first time that we see a delay in the measurements of these wavelengths,” said Yusef-Zadeh. “We notice that the longest wavelength is delayed between three and 40 seconds.” This finding is a key clue that energy particles lose energy as they cool, a process known as syncrotron cooling.
New observations. Researchers now plan to make a continuous observation of up to 24 hours from SGR A* using the Webb Telescope, which will help them determine if eruptions follow repetitive patterns or if they are truly random.
Each flash and every flicker on the accretion disk of the supermassive hole offers us a deeper understanding of physics on the events horizon, one of the most extreme environments in the universe. In other words, it helps us discover how space-time and matter behave under the influence of overwhelming gravity.
Image | NASA, ESA, CSA, RALF CRAWFORD (STSCI)
In WorldOfSoftware | The Webb Telescope has managed to penetrate the nucleus of a neighboring galaxy, home to a furiously active black hole
In WorldOfSoftware | Telescopes from all over the world worked together in this image: the black hole of the Milky Way and its magnetic fields
