AST-1A Chapter Notes - Chapter 17: Elliptical Galaxy, Spiral Galaxy, Galaxy Formation And Evolution
Document Summary
Observations allow is to observe key aspects of how galaxies evolve. The father we look in the universe, the further back we look in time. Most distant galaxies place by about 13 billion years ago: when most galaxies began to form. Galaxies lookback time is directly related to its age. Allowing us to see different stages of development. We cannot yet observe the earliest stages of galaxy formation, but we can rely on theoretical models with 2 key assumptions: Hydrogen and helium gas filed all of space almost uniformly. Distribution of matter in the universe was not perfectly uniform formed. We can use laws of physics and computer simulations to model how galaxies are. Also explains the formation of spiral galaxies: collapsing progalactic clouds. Supernovae of these massive stars seeded the rest of the progalactic cloud. Heating slowed the collapse and the rate at which stars formed radiated away their thermal energy cooling as they contracted.
