Download ASTR 1020: Stars & Galaxies - Exam 3 Preparation and Dark Matter - Prof. Jack O. Burns and more Study notes Astronomy in PDF only on Docsity! 1 1 ASTR 1020: Stars & Galaxies April 14, 2008 • Exam 3 next class, Wednesday, April 16th. • Extra credit: Fiske Planetarium shows every Thursday and SBO observing. 2 Exam #3 on April 16th • Study with a buddy! • Chapters 19.3-19.4, 20, 21, and 22.1-22.3. • Review notes on class website, MasteringAstronomy assignments, clicker questions, key concepts. • Same format: 20 multiple choice questions, 5 true-false and 3 short-answer questions. • Review sheet on CULearn. • Review session during recitations. 3 Be sure to bring to Exam • A number 2 pencil. • Your CU ID. • One page (front and back) of notes for the exam. • A calculator. 4 Astronomy Picture of the Day James Webb Space Telescope Mirror = 6.5 meters Launch = 2013 5 Last Time • Evidence for Dark Matter- galaxies, galaxy clusters • Dark matter vastly outweighs normal “baryonic” matter • Most likely a subatomic particle (wimps) - as yet unidentified! 6 Clicker Question: Dark Matter is inferred to exist because a) We see lots of dark patches in the sky b) It explains how the expansion of the universe can be accelerating c) We can observe its gravitational influence on visible matter 2 7 Clicker Question: Dark Matter is inferred to exist because a) We see lots of dark patches in the sky b) It explains how the expansion of the universe can be accelerating c) We can observe its gravitational influence on visible matter 8 Today • Chapter 22, Section 4: Dark Matter and the fate of the Universe. • On Friday: Dark Energy 9 Dark Matter and the Fate of the Universe • Expansion begins with the Big Bang • Several different models for Past and Future 10 Important Diagram • “Average distance between galaxies” = 1 / expansion factor =1 / (1+z) • NOW is fixed in time (z=0) • Hubble constant NOW sets the slope of the line = how fast the universe is expanding NOW Big Bang= when distance is zero; z=infinity 11 • But the expansion rate is not necessarily constant for all time…. • Gravity will SLOW expansion rate deceleration • Different models for different amounts of dark matter 12 Model Universes: Recollapsing Universe Dark matter density is greater than “critical density” (~ 10-29 grams/cc = a few atoms in a closet) Expansion will stop in the future, will collapse Oscillation?
