The heart of the galaxy known as M87 is a place of unimaginable violence. A black hole about six-and-a-half billion times as massive as the Sun sits at the galaxy's center -- one of the most massive black holes ever measured. As gas spirals into the black hole, it's heated to millions of degrees, so it produces enormous amounts of X-rays. Some of the hot gas around the black hole shoots back into the galaxy in powerful jets that span thousands of light-years.

M87 is at the center of the Virgo Cluster, a collection of thousands of galaxies that move through space together. It is a giant elliptical galaxy, so it's shaped like a fat, fuzzy watermelon. M87's diameter is only a little bigger than the Milky Way's, but because the galaxy is thicker than the thin disk of the Milky Way, it encompasses a much larger volume. As a result, M87 contains many more stars and is perhaps 10 times as massive as the Milky Way.

Several lines of evidence suggested that M87's core contains a supermassive black hole. (In fact, it was one of the first galaxies suspected to have a black hole, based on observations conducted in the early 1980s.)

First, observations with Hubble Space Telescope revealed that the core contains staggering numbers of stars -- thousands of times more than astronomers would normally expect to see even in the crowded center of a galaxy. Hubble also detected clouds of gas orbiting the center of the galaxy at very high speeds. These clouds form a spiral pattern, like the shape of the Milky Way. The stars and gas clouds are probably pulled into the center of the galaxy by a compact, dense object -- like a supermassive black hole.

And second, both optical and radio telescopes reveal the jets of hot gas that shoot into space at 99 percent of the speed of light. The jets probably form as powerful magnetic fields focus some of the superhot material just outside the black hole into two beams. The jets hold together for about 6,000 light-years before they really begin to slow down and spread out. Eventually, the expanding, cooling gas forms two big bubbles that each span about 200,000 light-years -- twice the diameter of our own Milky Way galaxy.

Finally, in 2019 the Event Horizon Telescope, a collaboration of observatories around the world, unveiled an image of M87--the first direct image of any black hole. It shows the "shadow" of the event horizon surrounded by the glow of background radiation that is bent and amplified by the black hole's gravity. The image, along with other observations, show that the black hole is roughly 6.5 billion times the mass of the Sun, making it one of the heaviest galaxies yet discovered.

Please follow the below links for previous chapters :-

Chapter 1 - Revealing the secret of Black Hole

Chapter 2 - Observational History of Black Hole

Chapter 3 - If falling into a Black Hole

Chapter 4 - Death by spaghettification of black hole

Chapter 5 - Mystery of monster black hole

Chapter 6 - Crossing a wormhole : reality of fiction?