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UA - PH/AY 101 - Class Notes - Week 9

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UA - PH/AY 101 - Class Notes - Week 9

School: University of Alabama - Tuscaloosa
Department: Astronomy
Course: AY 101 - Intro to Astronomy - Jeremy Bailin
Professor: Jeremy Bailin
Term: Spring 2015
Tags:
Name: AY 101 - Oct 18 Lecture Notes
Description: Lecture Notes from Tuesday, October 18, 2016
Uploaded: 10/18/2016
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background image AY 101 – OCTOBER 18 LECTURE NOTES    The sun shines equivalent to 4 trillion trillion 100W light bulbs 
  Where does the energy come from? 
o  Chemical reactions (combustion) could power it for 7500 years 
o  Gravitational contraction (turning gravitational potential energy into thermal by 
shrinking) could power it for 25 million years  o  Nuclear reactions can power it for 10 billion years  Age of the Solar System    Radioactive dating 
  Unstable isotopes break apart into stable isotopes 
  Half-life: how long does it take for half of the sample to decay? 
Radioactive Dating    Ratios of different lead (Pb) isotopes tells us the age 
  Result for Solar System objects: 4.54 billion years 
The Structure of the Sun    Hydrostatic Equilibrium 
  To balance more weight, gas is under higher pressure as you go inward 
o  = higher temperature + higher density      Nuclear Force – strong nuclear force can hold two like particles together, but only if they are  almost touching  o  Requires very high density and temperature  Mass is Energy    A consequence of Einstein’s Theory of Special Relativity: mass is a type of potential energy  o  E = mc^2    Speed of light c is large, so a little mass corresponds to a lot of energy 
  Every second in the sun 
o  600 million tons of Hydrogen  596 million tons of Helium + Lots of thermal energy    Thermal energy keeps the sun hot    Photosphere – Sun’s appear to be “surface”    Density low enough for photons to escape, but still not a solid surface 
  Light we see mostly comes from this region 
The Sun’s Absorption Lines    Kirchoff’s Laws: Absorption lines mean a hot dense gas behind cooler diffuse gas 

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School: University of Alabama - Tuscaloosa
Department: Astronomy
Course: AY 101 - Intro to Astronomy - Jeremy Bailin
Professor: Jeremy Bailin
Term: Spring 2015
Tags:
Name: AY 101 - Oct 18 Lecture Notes
Description: Lecture Notes from Tuesday, October 18, 2016
Uploaded: 10/18/2016
2 Pages 17 Views 13 Unlocks
  • Better Grades Guarantee
  • 24/7 Homework help
  • Notes, Study Guides, Flashcards + More!
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