Posted on June 17 inastrophysical journal lettersIn a recent paper in , William-D-Laughlin members Lena Murchikova of the Institute for Advanced Study, Chris White of Princeton University, and Sean Ressler of the University of California, Santa Barbara were able to use this subtle flicker to construct so far. The most accurate model yet of the central black hole of our own galaxy, Sagittarius A* (Sgr A*), provides insight into properties such as its structure and motion.
For the first time, researchers have shown in a single model the full story of how gas travels at the center of the Milky Way — from being blown by a star to falling into a black hole. By looking at the flickering light, the team concluded that the most likely scenario for the “feeding” of the black hole at the center of the Milky Way involves gas entering directly from a distance, rather than slowly pumping out orbital material over a long period of time.
“Black holes are the ‘gatekeepers’ of their own secrets. To better understand these mysterious objects, we rely on direct observations and high-resolution modeling,” Murchikova said.
While the existence of black holes was predicted by Karl Schwarzschild about 100 years ago based on Albert Einstein’s new theory of gravity, researchers are only now beginning to detect them through observations.
In October 2021, Murchikova published a paper in The Astrophysical Journal Letters describing a method to study the flickering of black holes on a time scale of seconds, not minutes. This advance allowed the researchers to more accurately quantify the properties of Sgr A* based on its blinking.
White has been studying the details of what happens in the gas near black holes (where the strong effects of general relativity matter) and how this affects the light that comes to us. Some of his findings were summarized earlier this year in The Astrophysical Journal.
Ressler has spent years trying to build the most realistic simulation yet of the gas surrounding Sgr A*. He did this by incorporating observations of nearby stars directly into the simulation, and meticulously tracking the material they shed as they fell into the black hole. The results of his most recent work have previously been published in The Astrophysical Journal.
Murchikova, White, and Ressler then collaborated to compare the observed blinking patterns of Sgr A* with those predicted by their respective numerical models.
“It turned out to be very interesting,” explains Murchikova. “For a long time, we thought we could largely ignore where the gas around a black hole came from. Typical models envision an artificial ring of gas, roughly doughnut-shaped, at some large distance from the black hole. We It was found that the flickering patterns produced by this model were inconsistent with the observations.”
Ressler’s stellar wind model takes a more realistic approach, where the gas consumed by black holes is initially shed by stars near the center of the Milky Way. When this gas fell into the black hole, it reproduced the correct blinking pattern. Ressler commented: “This model was not built to explain this particular phenomenon. Success is by no means a guarantee. So it is very encouraging to see the model succeed so dramatically after years of work.”
“When we study the flicker, we can see changes in the amount of light that the black hole emits every second, taking thousands of measurements over the course of a night,” explains White. “However, this doesn’t tell us how the gas is arranged in space like a large-scale image would. By combining these two types of observations, it’s possible to mitigate the limitations of each to get the most realistic picture.”
