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Stars

Stars. Star field taken with Hubble Space Telescope. Hertzsprung –Russell diagram. Pleiades. Star. Massive, luminous ball of plasma Held together by gravity Shines due to thermonuclear fusion of hydrogen in its core. Betelgeuse. Spectra of stars.

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Stars

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  1. Stars Star field taken with Hubble Space Telescope

  2. Hertzsprung–Russell diagram

  3. Pleiades

  4. Star • Massive, luminous ball of plasma • Held together by gravity • Shines due to thermonuclear fusion of hydrogen in its core

  5. Betelgeuse

  6. Spectra of stars Allow astronomers to determine a star’s: • Composition • Luminosity • Velocity • Mass

  7. Spectrum of the Sun

  8. 3 types of spectra

  9. Continuous- produced by a glowing body • Absorption line (dark line)- produced when a cooler gas lies between observer and glowing body – this is the type used to ID stars • Emission line (bright line)- emission from a glowing gas, used to study nebulae

  10. Star classification • Stars are all made of the same material • Spectral differences are due to temperature

  11. Coolest stars are red, hottest stars are blue

  12. Classification system • O B A F G K M • O hottest • M coolest

  13. H R (Hertzsprung Russell) Diagrams Stars plotted according to: • Luminosity (absolute magnitude) – brightest stars at the top • Temperature (spectral class) – hotter stars to the left

  14. H R Diagram (cont.) • Main sequence • Band from hot (blue) to cool (red) • 90% of stars • e.g. the Sun • Giants • Luminous and cool • 10-100x size of the Sun • e.g. Aldebaranin Taurus

  15. Super Giants • 1000x larger than the Sun • e.g. Betelguese in Orion Antares in Scorpius

  16. White Dwarfs • Very hot, but low luminosity due to small size • e.g. Sirius B • NO fusion in core, glow due to contraction? Gravitational forces

  17. Binary star • http://www.astronomy.ohio-state.edu/~pogge/TeachRes/Movies162/#spbin • http://www.calvin.edu/~lmolnar/anim/algol.html

  18. Albireo (the Cal star)

  19. Stellar Evolution

  20. Fusion

  21. Carbon-carbon fusion

  22. supernova

  23. http://www.pbs.org/wgbh/nova/origins/program-3114.html

  24. http://www.youtube.com/watch?v=8CtjhWhw2I8

  25. Stellar Evolution • Stars do not live forever • Eventually nuclear fuel runs out and star dies

  26. Stages of Stellar Evolution • Pre-main sequence • Stars form in a dense, cool cloud of dust and gas • Gravitational attraction causes it to start to glow • NO fusion yet  Protostar

  27. Once fusion starts the star enters the main sequence

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