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Classificagtion of Stars: The H-R diagram

“ The stars are distant and unobtrusive, but bright and enduring as our fairest and most memorable experiences.” Henry David Thoreau (1849). Classificagtion of Stars: The H-R diagram. Are Stars similar to our Sun? How far away are they? Where did they come from? What do they do?

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Classificagtion of Stars: The H-R diagram

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  1. “The stars are distant and unobtrusive, but bright and enduring as our fairest and most memorable experiences.” Henry David Thoreau (1849) Classificagtion of Stars:The H-R diagram Are Stars similar to our Sun? How far away are they? Where did they come from? What do they do? Do they live forever?

  2. Reading Assignment • All Chapter 9

  3. Discussion Question How can I understand the performance of CARS P = P(Weight; Power; Overall Built) Make a plot that shows the general relationship between Weight and Horsepower of cars. • now add to your plot sports cars… • … racing cars… • … and economy models This kind of plots summarizes in a powerful way general features of most cars

  4. Classification of Stars • Collect information ona large sample of stars. • Measure their luminosities(need the distance!) • Measure their surface temperatures(need their spectra)

  5. The Hertzsprung-Russell Diagram

  6. The Hertzsprung-Russell Diagram

  7. The Hertzsprung-Russell Diagram The Main Sequence - all main sequencestars fuse H into Hein their cores - this is the definingcharacteristic of a main sequence star.

  8. The Hertzsprung-Russell Diagram Red Giants - Red Giant starsare very large, cooland quite bright. Ex. Betelgeuse is100,000 times moreluminous than the Sunbut is only 3,500K onthe surface. It’s radiusis 1,000 times that of theSun.

  9. The Hertzsprung-Russell Diagram

  10. The Hertzsprung-Russell Diagram White Dwarfs - White Dwarfsare hot but sincethey are so small,they are not veryluminous.

  11. More mass,more fuel,very fast burning. Less mass,less fuel,slow, steady burning. The Hertzsprung-Russell Diagram Shorter Lifetimeof Star Longer Think SUV vs a Honda Civic How do we know the age of a star?

  12. O The H-R diagram • Which is the faintest? the sun, an O star, a white dwarf, or a red giant? • Which of these star is the hottest? • What are Sun-like stars (0.4 Msun < M < 8 Msun) in common? • What about red dwarfs (0.08 Msun < M < 0.4 Msun) ? • Where do stars spend most of their time? What is the order of stellar evolution of a star like the Sun?

  13. L=4πR2 σT4 To calculate a star's radius, you must know its 1) temperature and luminosity. 2) chemical composition and temperature. 3) color and chemical composition. 4) luminosity and surface gravity.

  14. L=4πR2 σT4 If a star is half as hot as our Sun, but has the same luminosity, how large is its radius compared to the Sun? 1) ½ times as large 2) ¼ times as large 3) 4 times larger 4) the same

  15. What is burning in stars? • Gasoline • Nuclear fission • Nuclear fusion • Natural gas

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