13: Galaxies Last updated Save as PDF Page ID 64063 Lumen Learning Lumen Learning 13.1: Module Introduction 13.2: What do you think? 13.3: Galaxies 13.4: The History of Studying Galaxies 13.5: Hubble’s Major Contributions 13.6: Hubble’s Law 13.7: Classification of Galaxies 13.8: Elliptical Galaxies 13.9: Spiral Galaxies 13.10: Irregular Galaxies 13.11: Active Galaxies 13.12: Quasar-stellar Objects 13.13: Blazars- Quasar-like Object 13.14: Galaxies, Distance, and Age 13.15: The Ages of Galaxies and What that Reveals 13.16: Galactic Groups 13.17: Dark Matter 13.18: WIMPs and String Theory 13.19: Gravitational Lensing