It can be seen from the above three-dimensional schematic diagram that when observing SgrA*, it is necessary to look into the Milky Way. The light has passed through the disk of the Milky Way and is affected by the higher density of interstellar matter; while when observing M87, when looking outside/up the Milky Way, the path directly passes through the disk of the Milky Way. , the light only passes through the lower density of interstellar matter. 1_f0lkfJuxrBade5XDT7z3EA Image provided by author Example image of scattering. Scattering occurs when light passes through interstellar matter. Light will be affected by ionized particles (such as electrons) and deviate from its original trajectory, and a "point of light" will thus become a "bulk of light".
Observing Sgr A is like shooting fireflies in front of neon lights, with too much background noise making it difficult to see the subject. Scientists need to remove the effect of scattering from the collected data to restore the true black hole appearance, but there will inevitably be distortions in the process. Two: imaging is more difficult 0_YXzWYCZa05fL4ds_ Image credit: Yukterez (Simon Tyran, Vienna), Wikimedia Commons, CC BY-SA 3.0 DE The path of a particle number list around a spinning black hole Both M87 and Sgr A* are spinning black holes. As the black hole rotates, the structure of its outer edge changes over time. We call the time at which changes are perceived as Variability timescales, which are bounded by values between 4 π tg and ~29.4 π tg (tg ≡ GM/c³). The M87 weighs 6.5 billion M☉  , while the Sgr A* weighs 4 million M☉, more than 1,500 times lighter than the M87. Substituting into the equation yields a variation time scale of about 5 days to 1 month for M87,
while it is only about 4 to 30 minutes for Sgr A*. The longer time scale of the M87 ensures that it is constant from shot to shot, but the Sgr A* is constantly changing over the course of a shot, so that every shot taken is different. 1_k8NYk9Qkc1-cjlL3JS0kxQ Image credit: Clustering and averaging the images of Sagittarius A* and M87* Screenshot above. Photos taken under different conditions on the left are combined into the image on the right. Since the Sgr A* photos taken each time are different, we can only see the partial truth like a blind man touching an elephant. In order to solve this problem, scientists have spent a long time building computational models, in a similar way to "average", to produce final representative images. Taking the shooting of snowy mountains as an example, in order to reduce the impact of the environment on the photo, we can choose to take a photo of it under different conditions (such as different times, weather, etc.), and synthesize it into a photo in an appropriate ratio. After retaining the common points and fading away the differences, the images are closer to reality.