Black Hole
A black hole is an astronomical object whose gravity is so strong that nothing—even light—can escape from within its event horizon. It forms when a massive star’s core collapses or through other processes, and may have an accretion disk of infalling matter that emits radiation. Supermassive black holes at galaxy centers influence stellar orbits, and mergers produce gravitational waves.
Source: nasa.gov
APODs including "Black Hole"
Streaming From A Black Hole
13/06/1997
Glowing gas clouds are streaming from the core of galaxy NGC4151 at hundreds of thousands of miles per hour. A powerful tool, the Hubble Space Telescope's new STIS instrument, makes it possible to map out the cloud velocities - producing this false color "velocity map" for the central regions of NGC4151. The horizontal line is light from the intensely bright region near the galaxy nucleus. Emission at two wavelengths characteristic of Oxygen atoms in the gas clouds is visible along this line. Below the line the emission is displaced to the left, indicating motion toward us (blue shift); above the displacement is to the right indicating a receding motion (red shift). Where do the clouds come from? As evidence mounts, the widely accepted explanation for energetic nuclear activity in galaxies is based on material spiraling into a central black hole with over a million times the mass of our sun. The rotating disk of interstellar debris which develops is thought to blast out high velocity jets along the axis of the disk. Do all galaxies contain supermassive black holes?