1. The Stars Chapter 14 Great Idea: The Sun and other stars use nuclear fusion reactions to convert mass into energy. Eventually, when a star’s nuclear fuel is depleted, the star must burn out.

2. The Nature of Stars Astronomy –Oldest science Star –Fusion reactor in space –Ball of gas All stars have a beginning and an ending

3. Measuring the Stars with Telescopes and Satellites Electromagnetic radiation Measurement of photons –Wavelength –Intensity –Direction –Variation

4. The Structure of the Sun Structure –Stellar core (hottest part, dense gas in a plasmic state) –Convection zone (rising gas from the core that cools) –Photosphere (the region from which externally received light originates) –Chromosphere (red color, thin layer, hotter and more dense than the photosphere) –Corona (external plasma atmosphere that extends hundreds of thousands or millions of miles into space) Solar wind –Stream of charged particles ejected from the upper atmosphere

5. The Sun's Chromosphere and Corona

6. Earth’s Magnetic Field

7. Northern Lights

8. The Sun’s Energy Source: Fusion Sun’s energy source Hydrogen (1 proton) converted to helium (2 protons) Life expectancy is 11 billion years, and the sun is currently 4.5 billion years

9. The Astronomical Distance Scale Time –Light-years (about 8,000 miles per second, or 6 trillion miles in 1 year) –The closest star to our sun is Proxima Centauri at 4.3 light years away (25.8 trillion miles) Measurement –Triangulation –Cepheid variable

10. The Hertzsprung-Russel Diagram Star groupings –Main-sequence stars –Red giants –White dwarfs

11. The Birth of Stars Nebular hypothesis –Pierre Laplace (gaseous clouds called nebulae rotate, cool, and gradually collapse and flatten due to gravity to form stars and planets)

12. The Eagle Nebula

13. Formation of a Planetary System

14. The Main Sequence and the Death of Stars Stars much less massive than the Sun –Brown dwarf –Glows 100 billion years No change in size, temperature, energy output

15. The Main Sequence and the Death of Stars – cont. Stars about the mass of the sun –Hydrogen burning at faster rate Move off main sequence –Helium burning –Red giant –Begin collapse –White dwarf

16. The Life Cycle of the Sun

17. Just how big are the stars?

18. The Main Sequence and the Death of Stars – cont. Very large stars –Successive collapses and burnings –Iron core –Catastrophic collapse Supernova

19. Star Explosion

20. Black Holes Black hole –Result of collapse large star –Nothing escapes from surface –Cannot see them See impact on other stars Detect x-rays, gamma rays

21. Cosmology Chapter 15 Great Idea: The universe began billions of years ago in the big bang and it has been expanding ever since.

22. Galaxies

23. Edwin Hubble and the Discovery of Galaxies Hubble –Largest telescope –Used Cepheid variable stars to measure distance to nebula Galaxies –Hubble discovered universe is billions of galaxies Cosmology

24. Kinds of Galaxies Spiral Elliptical Irregular and dwarf Active galaxies –Quasars

25. A Map of the Milky Way

26. A Typical Spiral Galaxy

27. A Typical Elliptical Galaxy

28. How BIG is the Universe??

29. The Redshift and Hubble’s Law

30. Redshift Hubble’s Law –The more distant a galaxy, the faster it recedes –V = H x d

31. Photographs of Galaxies and Their Spectra

32. What is the redshift??

33. Illustration of Hubble Expansion

34. The Big Bang

35. Big Bang –The universe began at a specific time in the past, and it has been expanding ever since

36. The Large-Scale Structure of the Universe The Local Group –Milky Way, Andromeda Galaxy, and others Groups, clusters, superclusters Voids

37. The Sequence of “Freezings”

38. 10 –43 Second: The Freezing of All Forces Two fundamental forces –Gravity –Strong-electroweak force Limit of our knowledge of universe

39. Dark Energy

40. What is Dark Energy?