9. What is a Black Hole?
If the remaining material of a star is even more than that of a neutron star, then the core is helpless and is incapable of preventing total gravitational collapse. At this stage even the repulsion between nuclei is overcome by gravity and the core collapses to a singularity, referred to as a black hole.
 NASA |
This image, captured by the Hubble Space Telescope, suggests that there is a black hole located in the magnified region. The black hole itself cannot be seen, but the matter falling into the blackhole emits radiation that can be detected.