What are the signatures of a Supernova to an astronomical observer?
1. Seen from Earth, the astronomers see a alowly brightening of the star over several months as the supernova's envelope is blasted outward by the shock wave. As days pass, the cloud of gas from a supernova explosion expands, thins, and fades.
2. Seen from Earth, the astronomers see a fast brightening of the star over several days as the supernova's envelope is blasted outward by the shock wave. As months pass, the cloud of gas from a supernova explosion expands, thins, and fades.
3. Seen from Earth, the astronomers see a fast brightening of the star over several days as the supernova's envelope is blasted outward by the shock wave. The brightening object suddenly fafdes away over a timescale of hours.
4. Seen from Earth, the astronomers see a fast brightening of the star over several years as the supernova's envelope is blasted outward by the shock wave. As tens of years pass, the cloud of gas from a supernova explosion expands, thins, and fades.