Last year, astronomers released the first-ever shadow image of the black hole event horizon at the center of the galaxy M87. It was made by the Event Horizont Telescope. We will never see the image of the black hole itself, because these objects have such powerful gravity that they absorb light that can illuminate them, and therefore remain in the shadows.
The image from the Event Horizont Telescope was an introduction to more advanced research of black holes, i.e. the most mysterious objects filling the space of the Universe. Now a group of scientists led by Maciej Wielgus, a Polish astronomer working at the Harvard-Smithsonian Center for Astrophysic, has examined the historical data from 2009-2013 on the M87 black hole.
It should be emphasized here that these data have never been published. The image of the black hole at the center of the galaxy M87 was made by EHT on the basis of only a week's observation, while scientists wanted to know if we could somehow trace the black hole's evolution over the years. It turns out that it is possible. They just did.
Maciej Wielgus and his team checked whether the semicircular shape of the event horizon would also be consistent with archival data. This is a fundamental question, as it can show us whether the picture is actually false. Astronomers have published a research paper on this topic in the prestigious The Astrophysical Journal.
The EHT observations made on the prototype matrices in 2009-2013 are not as accurate, but using statistical modeling, comparing geometric patterns and analyzing the information obtained, they found out that the shadow diameter of the black hole remained consistent with the predictions of Albert Einstein's general relativity for a black hole with a mass of 6.5 billion solar masses. The overall morphology or presence of an asymmetric ring persists over the years.
Interestingly, while the diameter of the event horizon's crescent moon remained the same, astronomers found that the bright ring rotated over the few years of observation. It looks as if the crescent moon is swaying. This is due to the turbulent flow of gas falling into the black hole. Astronomers will study data obtained by EHT, and also intend to make further observations with the participation of new telescopes, including currently under construction in Greenland.