That's because they actually observed it.
A very small region at the center of M87 releases an enormous amount of energy.
There is actually quite strong evidence for such a black hole - both from x-ray observations, and by observing the movement of nearby stars. The movements of nearby stars indicate that they are orbiting an object with about 4 million solar masses, and since this mass is concentrated in a very small space (the apoapsis of some of those stars is fairly close to the object), the only reasonable explanation, according to current astronomical knowledge, is a black hole.
Astronomers hypothesize that there's a supermassive black hole at the center of our galaxy, the Milky Way, both because of physical theory about the formation of galaxies, and direct observation from our own and other galaxies. Recent observations, focused on the behavior of stars very close to the nucleus of the Milky Way, led to a somewhat compelling conclusion: various stars at the galactic core could be tracked orbiting an object which was itself not directly observable (consistent with a black hole). The simple fact they were in orbit indicated the presence of a massive object. The maximum radius of the object they were orbiting had to be inside the closest approach of the nearest star in orbit, hence placing an upper limit on the radius of the object. The orbital radius and orbital period of the stars provided limits for the measurement of the amount of mass present in the object they orbited. Since the lower limit of the mass had to fit inside the maximum radius that the stars didn't collide with, the only object fitting the observations would be a supermassive black hole, of a little over four million solar masses.
One theory suggests that a black hole (a collapsed star with immense density) is located in the center of the galaxy. Another theory suggests that there's a wormhole leading to a whole other universe or dimension.
They spotted a bunch of stars orbiting around in the center at crazy speeds around what appears to be nothing but the only thing that could have that much mass to swing those stars around like moons would have to be insanely dense which could only be justified by being a super massive black hole
A very small region at the center of M87 releases an enormous amount of energy.
The very center is believed to contain a very powerful black hole.
A blazar is an elliptical galaxy with a supermassive black hole at the center.
A Supermassive black hole .
The supermassive blackholes at the center of galaxies.
Hypothesis are just well educated guesses. They think that because what else has enough gravity to hold in millions of billions of stars, planets, solar system. The only answer that we can understand at the moment would be that supermassive black holes hold together galaxys. There is also a small compilation of pictures showing stars moving at very very high speeds around a central object. One that we can only guess is a supermassive black hole.
It seems that just about EVERY galaxy has a huge ("supermassive") black hole in its center.
Not much actually. Scientists are still looking into it. What they do know though is that it has eaten up everything around it. Because of that, the supermassive black hole exists in a pitch black, empty area in the center of the Milky Way.
There is actually quite strong evidence for such a black hole - both from x-ray observations, and by observing the movement of nearby stars. The movements of nearby stars indicate that they are orbiting an object with about 4 million solar masses, and since this mass is concentrated in a very small space (the apoapsis of some of those stars is fairly close to the object), the only reasonable explanation, according to current astronomical knowledge, is a black hole.
I don't think there is a galaxy called "Satan A"; at least, not as a standard name, generally accepted by astronomers. On the other hand, most larger galaxies have a supermassive black hole at its center, and it can be expected that any galaxy has several stellar black holes.
Yes. In fact, it looks as if all, or most, larger galaxies have huge ("supermassive") black holes in their center. The largest black holes found so far have an estimated 20 billion solar masses.
Most astrophysicists believe that there is a supermassive black hole at the center of the Milky Way.