Why is a supernova faster than light? How did we see them and prove what they are made off?
Nothing is faster than light. Also not a supernova.Supernovae are the death throes of a massive star that has reached the end of its life. Nuclear fusion in the stellar core comes to a halt. The core collapses, and most of the star is blown into space — a Type II supernova. Type Ia’s are different: they occur when a white dwarf star gathers matter from a companion, passes a threshold mass, and detonates. Throughout the Milky Way, there are about two supernovae every 100 years.Such explosions are always accompanied by a huge burst of light - that’s how we detect them. Light is leaving the supernova (you guess it) at the speed of light.This artist’s impression shows a supernova explosion close-up. Credit: ESO/M. KornmesserIn both types of supernovae mentioned above a lot of material from the star is thrown into space. These expanding shells are known as supernova remnant. While these ejecta move fast (for us humans) with speeds of about 20 000 km/h, they are much slower than the speed of light - which is 300 000 km/s.(Note: first unit is given in km per hour, the speed of light in km per second!)Image of the Crab Nebula, taken with the NASA/ESA Hubble Space Telescope. The Crab Nebula is a supernova remnant.Credit: NASA, ESA and Allison Loll/Jeff Hester (Arizona State University). Acknowledgement: Davide De Martin (ESA/Hubble)
What is the difference between a quasar and a Supermassive black hole apart from the luminosity?
Before Hubble, quasars were considered to be isolated star-like objects of a mysterious nature. Hubble has observed several quasars and found that they all reside at galactic centres. Today most scientists believe that super massive black holes at the galactic centres are the "engines" that power the quasars.Quasars: The word quasar is short for "quasi-stellar radio source", which means star-like emitters of radio waves. Quasars also emit visible light, ultraviolet rays, infrared waves, X-rays, and gamma-rays. Quasars give off more energy than 100 normal galaxies combined. They are believed to be the most distant object detected in the universe to date. The amount of energy they give off can be up to a trillion times brighter than the sun! Quasars are located in black holes in the center of the galaxy. They are so bright their light drowns out the light from other stars. A quasar is approximately 1 kiloparsec in width and most of them are larger than our solar system.Black Hole: A black hole is a collapsed star. Its gravity is so strong that its escape velocity exceeds the speed of light. Since nothing is known to exceed the speed of light, nothing can escape from a black hole. Jets of hot gas are occasionally found streaming out of the region surrounding a black hole. There is an imaginary sphere around the black hole; it is known as the event horizon. Once matter reaches the inside of the event horizon, it is crushed into a single point and reaches infinite destiny-meaning it can never escape. There are three types of black holes: miniature black holes, supermassive black holes, and stellar black holes.
What is the difference between a supernova and a hypernova?
The simplest difference is that hypernovae are stellar explosions tens to hundreds of times more energetic than typical supernovae.The problem with otherwise explaining "the difference" is that at least three different mechanisms have been determined for hypernovae. One is the formation of high energy jets when the collapsing star is rapidly rotating. Apparently this will not happen with exploding stars that are originally rotating slowly.Another is a typical supernova explosion in a region containing a significant concentration of material beyond but near to the original star. Material from the supernova soon collides with this material and energizes it so that additional energy is radiated away.A third is something called pair-instability collapse in which a sudden high rate of production of electron-positron pairs leads to an accelerated collapse and subsequent explosion of the star. This apparently can only happen with stars of low metallicity characteristic of the earliest stars and then only when the original mass of the star is hundreds of times the mass of the sun. All of these hypernovae are necessarily at great distances from us, as they can't occur in later generation stars.Here's a more detailed description of the mechanisms: Hypernova