Lesson Four : Black Holes
Following a supernova explosion, if the remaining mass of the star's core exceeds twenty solar masses, it will form a black hole. A star this massive will continue to collapse even after it has reached its neutron star stage. The star can no longer hold up under its own gravity and condenses to an infinitely massive, infinitesimally small point in space called a singularity.Since the singularity is so massive, its gravitational field is incredibly strong and nothing that passes within its event horizon can escape its pull- not even light. As particles and waves spiral into a black hole, their charge particles generate electromagnetic radiaiton. They emit a final beam of energy covering the entire electromagnetic spectrum. The disk of matter falling into the black is hole is called an accretion disk and the radiation is emitted as two jets of energy on perpendicular to the disk.
A black hole surrounded by an accretion disk of infalling matter and emitting twin jets of energetic particles.
Black holes are some of the most intriguing objects in the sky. Scientists are certain that super massive black holes lurking within galactic centers are one of the reasons that galaxies hold together. Since nothing can enter a black hole and return, these objects remain one of the most interesting celestial phenomena.