On the right is the same star field but this time with a black hole superposed in the center of the frame. The black hole has such strong gravity that light is noticeably bent towards it - causing some very unusual visual distortion. In the distorted frame, every star in the normal frame has at least two bright images - one on each side of the black hole. In fact, near the black hole, you can see the whole sky - light from every direction is bent around and comes back to you. Black holes are thought to be the densest state of matter, and there is indirect evidence for their presence in stellar binary systems and the centers of globular clusters , galaxies , and quasars .
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