1 Cosmology HNRT 227 Chapter October 2015 Great Idea: The universe began billions of years ago in the big bang and it has been expanding ever since.

2 Chapter Outline Galaxies The Redshift and Hubble’s Law The Big Bang The Evolution of the Universe Dark Matter and Ripples at the Beginning of Time The End of the Universe

3 Galaxies

4 The Nebula Debate Nebulae –Cloud-like objects Shapley vs. Curtis –Debate over distance of nebulae

5 Edwin Hubble (with Milt Humason) and the Discovery of Galaxies Hubble –Largest telescope in his day –Used Cepheid variable stars to measure distance to nebulae Galaxies –Hubble examined a multitude of galaxies Categorized and measured Cosmology –All galaxies outside our Local Group are moving away from us Doppler shift

6 Kinds of Galaxies Spiral Elliptical Irregular (& Dwarf) Active galaxies –Blazars, Quasars, Radio, Seyfert

7 Properties of Galaxies Property Spirals Ellipticals Irregulars Mass/M of Sun 10 9 to 4x to to 3x10 10 Luminosity/L of Sun 10 8 to 2x x10 5 to to 3x10 9 Diameter (light years) 16x10 3 to 8x10 5 3x10 3 to 7x10 5 3x10 3 to 3x10 4 % of galaxies 77% 20% 3% National Optical Astronomy Observatory images From this table, consider which galaxies are the most and least massive, most and least luminous, and largest and smallest in size.

8 Active Galaxies

9 Hubble Deep Field

10 The Redshift and Hubble’s Law

11 The Redshift and Hubble’s Law Redshift Hubble’s Law –The farther a galaxy, the faster it recedes –V=H x d

12 The Big Bang

13 The Big Bang Big Bang –Best model of the formation of the universe –The universe began at a specific time in the past, and it has been expanding ever since

14 The Large-Scale Structure of the Universe The Local Group –Milky way, Andromeda galaxy, and others Groups (smaller number), clusters, superclusters –Regular and irregular Voids

15 Some Useful Analogies Raisin-Bread Dough Analogy Expanding Balloon Analogy

16 Evidence for the Big Bang The Universal Expansion –Steady-state universe The Cosmic Microwave Background –Penzias and Wilson End of steady-state theory The Abundance of Light Elements –Hydrogen, helium, very little lithium and beryllium

17 The Evolution of the Universe

18 Some General Characteristics of an Expanding Universe All matter heats when compressed –Hot big bang Freezings –Changes in universe

Second: The Freezing of All Forces Two fundamental forces –Gravity –Strong-electroweak force Limit of our knowledge of universe

Second: The Freezing of the Electroweak and Strong Forces Three fundamental forces The elimination of antimatter –Galaxy is ordinary matter –Why? Leftover protons Inflation –Short rapid expansion Common temperature

Second: The Freezing of the Weak and Electromagnetic Forces Four fundamental forces Particle accelerators –Reproduce from here forward –Experimental evidence for evolution of universe

Second: The Freezing of Elementary Particles Elementary particles formed Prior –Quarks and leptons After –Hadrons and leptons Electrons, protons and neutrons

23 Three Minutes: The Freezing of Nuclei Nuclei become stable Only nuclei of H, He, Li, Be Plasma

24 Before One Million Years: The Freezing of Atoms Formation of Atoms Radiation released –Cosmic microwave background Galaxy problem

25 Dark Matter and Ripples at the Beginning of Time Dark Matter –Measure gravitational effects Hydrogen atoms Formation of dark matter (questions to be answered) –Before atoms formed? –Formed clumps? Ripples at the beginning of time –Collection of luminous matter

26 The End of the Universe Open, closed or flat universe Current data –Mass of universe Open universe –Type Ia supernova Dark Energy –70% of universe’s mass Future –Depends on dark energy –Big Rip