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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
    • II. Size
      • Larger the star Brighter the Star
      • Smaller the star Dimmer the Star
    • 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