1. Stellar Evolution The Birth, Life, and Death of Stars

2. The Universe • Everything • All matter, space, and time • The Universe is 13.72 billion years old

3. Cosmology • The study of the origin of the Universe

4. The Sun • An average sized Star • About 4.5 billion years old

5. What is a Solar System? • A star and everything that revolves around it • Our Solar System is about ___ years old

6. A light-year • A unit of distance, not time • The distance light travels in one year • 6 Trillion miles

7. Distance to Sun • 93 million miles • 8.3 light-minutes

8. Proxima Centauri • The closest star to our sun • About 4 light-years away

9. Galaxies • Stars are not evenly distributed in space. • They are in groups called Galaxies.

10. Types and Sizes of Galaxies • Types: Elliptical, Spiral, Irregular • Two sizes • Giant • Dwarf

11. The Milky Way Galaxy • 100,000 light years across • Has Hundreds of billions of stars

12. Galaxy Clusters • A Group of Galaxies • Local Group • 2 mly across • 3 large & about 2 dozen dwarf • Andromeda 2.2 mly

13. Galaxy Superclusters • A cluster of clusters • The Local (Virgo) Supercluster • 100 clusters • 100 mly across

14. Nearest Superclusters

15. Galaxy Superclusters

16. The Visible Universe

17. How big is the Universe? • The visible universe is 28 billion light years in diameter. • Why is that all that is visible? • The entire universe may be much bigger

18. How many Galaxies are there? • Hundreds of billions • Each has hundreds of billions of stars

20. Edwin Hubble • 1920’s • Discovered other galaxies • Discovered the Universe is expanding

21. The Expanding Universe • The Red Shift • Doppler effect

22. The Doppler Effect

23. The Big Bang • Tremendous explosion started the expansion of the universe • All of the matter and energy of the universe was contained at one point

25. Characteristics of Stars

26. Star Properties and Classification • Color • Temperature • Age • Apparent brightness • Distance from Earth

27. Star Brightness • Apparent Magnitude • How bright it looks from Earth • Absolute Magnitude • How much light it actually produces

28. Apparent Magnitude (Brightness) • Depends on actual brightness (luminosity) and distance away

29. Hertzsprung-Russell (H-R) Diagram Compares a star’s Temperature (color) and its … • Absolute Magnitude (Brightness)

30. Hertzsprung-Russell (H-R) Diagram

31. Hertzsprung-Russell (H-R) Diagram • Things to Know • Color depends on temperature • Blue, White, Yellow, Orange, Red • The higher the Temperature the Brighter the Star (if in the main sequence) • White Dwarfs and Red Giants are exceptions • The Sun is in the main sequence (90% of stars)

32. Star Relative Size • The Sun is an averaged sized star

33. Stellar Evolution The Formation and Life Cycle of Stars

34. Star Formation • Originate in gas clouds in space called Nebula • Mostly Hydrogen • Gravity pulls it together

35. Nebula • The contraction heats the gases • When it gets hot enough (27 million degrees) nuclear fusion starts

36. Nuclear Fusion • Hydrogen nuclei are fused to make helium • The reaction produces heat energy, which causes more fusion

37. How big is a Nebula? • The Orion Nebula is about 2.5 light years across

40. Old Age • When the hydrogen runs low • Contractions make more heat • Causes nuclear fusion to make heavier elements • Expansion results in a Red Giant

41. White Dwarf • When energy is used, it shrinks to make a white dwarf

42. Supernovas • Collapses abruptly then explodes • Billions of times brighter • Creates heavier elements • Occurs only in very massive stars

43. After a Supernova • The outer layers are blasted into space to create a new nebula (starts the cycle over) • The core collapses to form a neutron star

44. Neutron Star • Left over after a supernova • 1 teaspoon weighs billions of tons

45. Black Holes • A star so dense, even light can not escape

47. Formation of Heavier Elements • Elements heavier than hydrogen are formed by nuclear fusion in Stars • Elements heavier then iron form during a Supernova

48. The End