AST 111 Lecture Notes - Lecture 22: Dark Matter, Spiral Galaxy, Cosmic Dust

• School: Tunxis Community College
• Department: Astronomy
• Course: AST 111
• Professor: Reynolds

Document Summary

Flat geometry implies that the total density of matter plus energy in the universe is equal to critical density. Observations show that matter only account for 30% of this critical density. 70% of critical density must be in the form of energy. Sure enough, the amount of energy needed to explain the observed acceleration of the expansion is 70% 70% of the total mass-energy of the universe is dark energy. Composition of the universe: 68% dark energy, 27% exotic dark matter, 5% ordinary matter. Models that explain dark energy also agree that the universe is almost 14 billion years old. Seems that the universe is doomed to expand forever, its galaxies receding ever more quickly into an icy, empty future. Eventually, star formation will stop as mass becomes locked up in planets, brown dwarfs, white dwarfs, neutron stars, and black holes, and galaxies will fade into the darkness.