Clicker Question. Double-header clicker. Joys of Observational Cosmology. A. Recollapsing. B. Critical. C. Coasting. A. Coasting. C.

Transcription

1 ASTR 1040 Accel Astro: Stars & Galaxies Large-scale structure CfA survey Prof. Juri Toomre TA: Kyle Augustson Lecture 29 Tues 29 Apr 08 zeus.colorado.edu/astr1040-toomre toomre Joys of Observational Cosmology Look further at models for our universe, and ideas of dark energy arising from white-dwarf supernova data + CMB mapping Next time: what occurs during big-bang bang beginning + galaxy structures Review Set # 4 now available (Final Exam on Mon 5 May, 1:30pm here) Course evaluation at end of class Which model predicts the greatest age for the universe today? A. Recollapsing (closed) B. Critical (flat) C. Coasting (open) Clicker Question C. C. Coasting Age of universe is how far to left curves hit horizontal axis (distance between galaxies = 0) Double-header clicker If there was really ZERO dark matter in the universe, which model would be the closest to reality? A. A. Coasting B. Critical C. Recollapsing Baryonic matter is only a few percent of the critical density Closest model would be the Coasting Model (no or little deceleration from gravity) 1

2 REMINDER Which is it? Is there enough dark matter to recollapse the universe? Baryonic matter: only few % of critical density Dark matter: only about 25 % of what is needed Universe is between the coasting and critical models Universe will expand forever (or so it seems) New twist in the new millenium White dwarf supernovae: standard candles at Z ~ 1 Explosions bright enough to be seen very far away (back in time) Made especially possible by HST Z = 1 means about halfway down from the NOW level Expansion factor = 1 + Z = 2 Redshifts of the supernova plot their vertical position Brightness plots their horizontal position Dimmer = more distant = longer ago Supernovae are DIMMER than expected for a coasting universe Universe is accelerating?? SIZE Models of universe and its fates OPEN CRITICAL (FLAT) How can universe be accelerating???? A force that counteracts gravity? NOW TIME CLOSED Dark energy outweighs every other form of mass/energy! Truly an unknown force in all of physics! (Read Einstein;s Biggest Blunder Cosmological Constant - p 695) 2

3 Another recent idea: INFLATION VERY EARLY: strong force becomes distinct, huge amount of energy released Universe INFLATES: atomic nucleus size to solar system size in sec DOES NOT COOL Motivating puzzle: Why is CMB so uniform? Inflation: coupling all portions of universe INFLATION needed to explain uniformity of CMB WMAP 0.3 degree resolution Small temperature fluctuations used to test models of universe one degree scale in sky --> flat universe with early inflation Boomerang: finer CMB mapping Boomerang mapping Balloon Mt Erebus Antartica 3

4 Curvature of universe and CMB pattern Our view of CMB to scale in sky CLOSED FLAT OPEN Boomerang Variations in CMB on small scales To get 1 degree peak, cosmology models involve FLAT geometry Best of the Crib Sheets Awards! This award, for the crib sheet with The Most Use of Color + Most Aesthetic Appeal Is presented to Margaret McNulty This award, for the crib sheet with The Most Economical use of Space Is presented to William Scott Hanes 4

5 What CMB ripples and distant SN imply about cosmology parameters This award, for the crib sheet with The Most Immaculate Scribing Is presented to Katlyn Foley current favorite values: How can universe be accelerating???? A force that counteracts gravity? Dark energy outweighs every other form of mass/energy With alarming new ideas like inflation and dark energy. Einstein deserved to be concerned! SIZE Models of universe and its fates NOW OPEN CRITICAL (FLAT) TIME CLOSED Clicker on our universe Which events had profound effects on our modern views of universe? D. A. Einstein devising General Theory of Relativity B. Penzias & Wilson detecting uniform CMB radiation from all directions C. Hubble finding that most galaxies are receding the Hubble law D. All of the above 5

6 Evolution of Universe 6