ASTR 1020 Chapter Notes - Chapter 21: Galaxy Formation And Evolution, Cosmic Dust, Starburst Galaxy
22 Apr 2017
School
Department
Course
Professor
Document Summary
Hydrogen and helium gas and dark matter filled space almost uniformly, but certain parts were slightly denser than others. Material in these denser parts contracted into protogalactic clouds. Hypothesis 1: elliptical galaxies may be different from spirals because of their different birth conditions. If a system had a lot of angular momentum, it would"ve spun rapidly as it collapsed, forming a disk. Fast rotation = disk, slow rotation = elliptical. Protogalactic clouds with greater density would"ve cooled down faster, allowing rapid star formation. The stars could"ve been formed before gas settled into a disk. More dense = elliptical, lense dense = disk. Hypothesis 2: elliptical galaxies start out the same as spiral galaxies, but later become elliptical through interactions with other galaxies. Galaxies are relatively close to each other, collisions happen often. Collisions between two spiral galaxies can form an elliptical galaxy, tidal forces tear apart the disks of the two galaxies.
