black hole
M87 is an active galaxy, one in which we see interesting objects. Near its core (or centre) there is a spiral-shpaed disc of hot gas. The first picture places it in context. The second superposes spectra from opposite sides. This allows us to determine the speed of rotation of the disk and its size. From this we can weigh the size of the invisible object at the centre.
Although the object is no bigger than our solar system it weighs three billion times as much as the sun. This means that gravity is so strong that light cannot escape. We have a black hole.
In the first figure, there is a diagonal line. This is believed to be the passage out of those fortunate particles which escape along the axis of rotation and avoid being swallowed by the black hole.
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a black hole 'no bigger' than our solar system? in some ways this is beautiful. in others, frightening.