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The Formation of Stars

The Formation of Stars. Chapter 11. Giant Molecular Clouds Large Low density Cold. To Form Stars Small High density Hot. 4 Factors that Resist Contraction. Thermal Energy Interstellar Magnetic Field Rotation Turbulence. Shockwaves. Caused by: Supernova Explosions

celestyn-leighton
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The Formation of Stars

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  1. The Formation of Stars Chapter 11

  2. Giant Molecular Clouds • Large • Low density • Cold To Form Stars • Small • High density • Hot

  3. 4 Factors that Resist Contraction • Thermal Energy • Interstellar Magnetic Field • Rotation • Turbulence

  4. Shockwaves Caused by: • Supernova Explosions • Ignition of very hot stars—can ionize nearby gas • Collisions of molecular clouds • Spiral Pattern of the Milky Way Galaxy

  5. How to get hot enough? Free-Fall Contraction • The cloud begins to contract as gravity pulls atoms to the center. • Increase in velocity = heating of gas • Increase in velocity leads to thermal energy

  6. Protostar • Definition: A prestellar object that is hot enough to radiate infrared radiation but not hot enough to generate energy by nuclear fusion. • Hidden by Cocoons • Emit infrared radiation • Located on the Birth line of the HR Diagram • 0.1% of star’s lifetime

  7. The CNO Cycle • The Hydrogen fusion process that used Carbon, Nitrogen, and Oxygen as stepping stones. • Used by main sequence stars with mass greater than 1.1 solar masses • Temperatures greater than 16 million K

  8. Carbon-12 nucleus absorbs a proton • Becomes nitrogen-13 • Decays into Carbon-13, absorbs a 2nd proton • Becomes Nitrogen-14, absorbs a 3rd proton • Becomes Oxygen-15 • Decays into Nitrogen-15, absorbs a 4th proton, ejects a He nucleus • Becomes Carbon-12

  9. Energy Transport • Conduction • Radiation • Convection

  10. Inside Stars • Upper Main Sequence Stars • More massive • CNO Cycle • Convective Zone in center • Lower Main Sequence Stars • Least massive • Proton-Proton Chain • Radiative Zone in center

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