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Stellar Evolution

Stellar Evolution. The Birth, Life, and Death of Stars. The Universe. Everything All matter, space, and time The Universe is 13.72 billion years old. Cosmology. The study of the origin of the Universe. The Sun. An average sized Star About 4.5 billion years old. What is a Solar System?.

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Stellar Evolution

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  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

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

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

  21. The Doppler Effect

  22. 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

  23. Characteristics of Stars

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

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

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

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

  28. Hertzsprung-Russell (H-R) Diagram

  29. 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)

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

  31. Stellar Evolution The Formation and Life Cycle of Stars

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

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

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

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

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

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

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

  39. 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

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

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

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

  43. The End

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