A unique process is occurring in the supermassive black hole Sagittarius A*, the center of our galaxy. A study published in Monthly Notices, a monthly journal of the Royal Astronomical Society, shows that black holes rotate at speeds close to their maximum possible speed. Measurements from NASA’s Chandra X-ray Observatory showed that its rotational speed is 0.84 to 0.96 times faster than the maximum possible speed of light. This discovery has important implications for understanding the formation of black holes and related astrophysical phenomena. The rotational speed of a black hole is measured from 0 to 1 (1 being the maximum speed) and is determined by its angular momentum and its interaction with its environment, including its accretion disk. What’s special about black holes is that their rotation affects the very fabric of space-time. Unlike planets and stars, black holes do not have physical surfaces, but regions of spacetime bounded by so-called event horizons. As a result, their rotation causes space-time to bend and twist significantly, forming the so-called ergosphere.
This phenomenon, known as “frame shift” or “lens Surling effect,” causes unusual visual effects such as gravitational lensing near black holes. The path of light passing near a rotating black hole is bent, forming a halo of light and even a shadow of the black hole. The theoretical limit to the speed of a black hole is determined by how the black hole consumes matter and thereby grows. As a black hole’s mass increases, its gravitational pull increases, making it more difficult to increase its speed. For example, the black hole at the center of galaxy M87 has a mass equivalent to 6.5 billion suns and rotates at 0.89 to 0.91 times the speed of light, while Sagittarius A*, which has a mass of about 4.5 million suns, Speed of light 0.84-0.96. This discovery highlights the uniqueness and importance of studying supermassive black holes for understanding the structure of galaxies and the astrophysical processes of the universe.
source: https://academic.oup.com/mnras/article/527/1/428/7326786