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"
The Long Jet of Pictor A
19/06/2000
A jet stretching nearly a million light years has been imaged emanating from galaxy Pictor A. The thin jet of electrons and protons shoots out at nearly light-speed likely from the vicinity of a large black hole at the galaxy center. At the left of the above image in X-rays is the radio galaxy Pictor A, known as a radio galaxy for its strong radio emission. At the far end of the jet on the right a hot spot glows as the intense particle beam bores through a gas cloud in intergalactic space. The jet and hot spot of Pictor A had been seen previously in radio waves, but only recently has the orbiting Chandra X-ray Observatory confirmed its unusual power.