3: The Universe Last updated Save as PDF Page ID12749 3.10: Star Classification3.11: Measuring Distant Stars3.1: Introduction to the Universe3.2: Video: The History of Our World in 18 Minutes3.3: Expanding Universe3.4: Formation of the Universe3.5: Dark Matter and Dark Energy3.6: Star Systems3.7: Types of Galaxies3.8: Milky Way Galaxy3.9: Star Energy