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life cycle of a star






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life cycle of a star life cycle of a star Presentation Transcript

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