life cycle of a star


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life cycle of a star

  1. 1. Life Cycle of a Star
  2. 2. Star Light, Star Bright
  3. 3. 3 Factors that determine the brightness of a star <ul><li>Temperature </li></ul><ul><li>Hotter the star the brighter the star </li></ul><ul><li>Blue…..white……..yellow…….orange…….….red </li></ul><ul><li>HOTTEST---------------------------------------COOLEST </li></ul>
  4. 4. II. Size <ul><li>Larger the star Brighter the Star </li></ul><ul><li>Smaller the star Dimmer the Star </li></ul>
  5. 5. III. Distance <ul><li>Closer the star Brighter the star </li></ul><ul><li>Further the star Dimmer the star </li></ul>
  6. 6. Brightness Key Terms <ul><li>1. Luminosity </li></ul><ul><li>2. Apparent Magnitude </li></ul><ul><li>3. Absolute Magnitude </li></ul><ul><li>4. Parallax </li></ul>
  7. 7. 1. Luminosity <ul><li>Definition- actual or true brightness of a star </li></ul><ul><li>Total amount of energy given off </li></ul><ul><ul><ul><li>Dependent on 2 things: </li></ul></ul></ul>Temperature 6000K 10,000K More luminous Size 6000K 6000K More luminous
  8. 8. 2. Apparent Magnitude <ul><li>Definition- how bright a star appears when seen from earth </li></ul><ul><li>System developed where a number is assigned to a star based on brightness </li></ul><ul><ul><ul><ul><li>Smaller number equals the brighter the star </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Bigger number equals the dimmer the star </li></ul></ul></ul></ul><ul><li>Examples are : Sun 28 , Full Moon 11, Polaris 7, Hubble can see +28 </li></ul>
  9. 9. 3. Absolute Magnitude <ul><li>Definition- brightness of a star as if all stars were seen from the same distance </li></ul>Earth Earth Sun- average star, Abs. Mag of +4.8 (less luminous, looks brighter because closer) Rigel- orion, Abs, Mag. of -6.4 (more luminous, further away) To Determine: apparent magnitude and distance to earth
  10. 10. Moving Stars? <ul><li>Parallax- the apparent change in position of a star due to the movement of observer </li></ul>Finger: left/right
  11. 11. Life Expectancy of a Star <ul><li>Low Mass Star </li></ul><ul><ul><li>200 B illion years </li></ul></ul><ul><li>Medium Mass Star (our Sun) </li></ul><ul><ul><li>10 B illion years </li></ul></ul><ul><li>High Mass Star </li></ul><ul><ul><li>10 M illion years </li></ul></ul><ul><li>The Mass of a star determines the length of it’s life. More Mass = Higher energy used = shorter life. </li></ul>
  12. 12. Life Cycle of a Star <ul><li>Nebula (low and high mass stars) </li></ul><ul><li>Protostar (low and high mass stars) </li></ul><ul><li>Main Sequence Star (low and high mass stars) </li></ul><ul><li>Red Giant (low mass stars) or Super Red Giant (High Mass stars) </li></ul><ul><li>White Dwarf (low mass stars) or Super Nova (high mass stars </li></ul><ul><li>Black Dwarf (low mass stars) or Neutron Star (high mass stars) </li></ul><ul><li>Black Hole (high mass stars) </li></ul>
  13. 13. All Stars <ul><li>1. NEBULA 1 st Stage of Life </li></ul><ul><ul><li>Ball of gas and dust that is pulled together by gravity. </li></ul></ul><ul><ul><ul><li>Gravity pulls cloud INWARD = causes increase of temperature. </li></ul></ul></ul><ul><ul><li>2. Protostar when the gases heat up enough to give off light. (still not a star yet ) </li></ul></ul>
  14. 14. <ul><li>3. Main Sequence </li></ul><ul><li>3 nd Stage of Life Nuclear fusion starts as gas cloud becomes denser and hotter. </li></ul><ul><ul><ul><li>The internal heat pressure OUTWARD balances the INWARD gravitational pressure. </li></ul></ul></ul><ul><ul><ul><li>Star STOPS collapsing and is STABLE. </li></ul></ul></ul><ul><li>Nuclear Fusion  hydrogen atoms fuse into helium </li></ul><ul><ul><li>Creates the intense energy found in stars. </li></ul></ul><ul><li>Longest stage of Life of Star </li></ul>
  15. 15. <ul><li>Our Sun is in the Main Sequence stage. </li></ul>
  16. 16. Hydrogen fuses into Helium in the Core. 4 H  1 He Creates great heat! E = mc 2
  17. 17. Fate determined by Size <ul><li>If a normal size star (Sun) follows path 1 </li></ul><ul><li>If star is a GIANT follows path 2 </li></ul>
  18. 18. <ul><li>Path 1 </li></ul><ul><li>Low/medium mass stars </li></ul>
  19. 19. Low/Medium Mass Star - Sun <ul><li>4. Red Giant </li></ul><ul><ul><li>4 th stage </li></ul></ul><ul><ul><ul><li>Main Sequence star expands to become a Red Giant. </li></ul></ul></ul><ul><ul><ul><ul><li>Due to shortage of fuel, hydrogen is fusing only in outer shell. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Outward pressure GREATER than Inward pressure = EXPANSION! </li></ul></ul></ul></ul><ul><li>Red giant  star that expands and cools. </li></ul><ul><ul><li>Due to NO hydrogen in the core. </li></ul></ul><ul><ul><li>Core shrinks and atmosphere grows large and cools = turns Red. </li></ul></ul>
  20. 20. <ul><li>The Sun will EXPAND beyond Mars. </li></ul><ul><ul><li>Swallowing up the Earth! </li></ul></ul>
  21. 21. Low/Medium Mass Star <ul><ul><li>5. White Dwarf </li></ul></ul><ul><ul><ul><li>Final stage: The Red Giant Collapsed! </li></ul></ul></ul><ul><ul><ul><li>Hot and Dim (hot due to collapse) </li></ul></ul></ul><ul><ul><ul><ul><li>Inward pressure GREATER than Outward pressure = COLLAPSE </li></ul></ul></ul></ul><ul><ul><ul><li>Outer shell escapes into space. (planetary nebula. </li></ul></ul></ul><ul><ul><ul><li>Can shine for billions of years before they extinguish. </li></ul></ul></ul>
  22. 24. Low/Medium Mass Star <ul><li>6. Black Dwarf </li></ul><ul><li>The sun cools more and more </li></ul><ul><li>Eventually it will become a black mass emitting no light </li></ul><ul><li>It will then spend the rest of eternity drifting silently through space </li></ul>
  23. 26. <ul><li>Path 2 </li></ul><ul><li>High Mass Stars </li></ul>
  24. 27. High Mass Star <ul><li>Begins from Nebula , evolves into Protostar then into a Massive Mainsequence star. </li></ul><ul><li>4. Super Giant Stage : </li></ul><ul><ul><li>Expands due to shortage of Hydrogen fuel but because of tremendous heat, fuses heavier elements. </li></ul></ul><ul><ul><ul><li>Causes higher heat so expands to larger size = Super Giant </li></ul></ul></ul><ul><ul><ul><li>Then runs out of fuel and cools = RED SUPER GIANT </li></ul></ul></ul>
  25. 30. High Mass Star <ul><li>5. SUPER NOVA </li></ul><ul><ul><li>The end is near! </li></ul></ul><ul><ul><li>As the Super Giant runs out of fuel . . . </li></ul></ul><ul><ul><ul><li>It’s core collapses which causes an EXPLOSION! </li></ul></ul></ul>
  26. 32. Supernova <ul><li>All the atoms we are made from came originally from these giant supernova explosions. </li></ul>
  27. 34. Super Massive Stars <ul><ul><ul><li>6. NEUTRON STAR </li></ul></ul></ul><ul><ul><ul><li>The core continues to collapse creating a Smaller than Earth </li></ul></ul></ul><ul><ul><ul><ul><li>1 teaspoon = 1 billion tons </li></ul></ul></ul></ul>
  28. 35. High Mass Star <ul><li>7. BLACK HOLE </li></ul><ul><li>Final Stage for High Mass Stars </li></ul><ul><ul><li>If massive enough, the Neutron star will continue to collapse on itself. </li></ul></ul>
  29. 37. <ul><li>Black Hole  an object that is so massive that light cannot escape its gravity </li></ul><ul><ul><li>Remnants of a supernova </li></ul></ul><ul><ul><li>Astronomers can detect black holes by using X-ray telescopes </li></ul></ul>
  30. 38. Life Cycle of Star http:// =YU6X3SPZAJo