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UA - PH/AY 101 - AY 101 - Midterm 3 Study Guide - Study Guide

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UA - PH/AY 101 - AY 101 - Midterm 3 Study Guide - Study Guide

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background image AY 101 – MIDTERM 3 STUDY GUIDE  Planetary Systems    Solar System is neither rare nor universal:  o  Some planetary systems are similar to the Solar System, with Terrestrial and Jovian  planets separated in radius, on circular orbits  o  Some systems are very different with Jovian planets on compact orbits and all planets  on very elliptical orbits    The Sun  o  The nearest star 
o  Contains 99.8% of the mass of the Solar System 
o  Study of absorption lines tells us composition: 
  71% hydrogen 
  27% helium 
  2% heavier elements (“metals”) 
o  Shining    About equivalent to 4 trillion trillion 100w light bulbs 
  Where does the energy come from? 
  Chemical reactions (combustion) could power it for 7500 years 
  Gravitational contraction (turning gravitational potential energy into 
thermal kinetic energy by shrinking) could power it for 25 million years    However, it’s already been burning for 4.5 billion years    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   
background image   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 
  Hot dense object is bottom of photosphere, cooler diffuse gas is top of the photosphere 
What might you find in the center of a core collapse supernova remnant?    Pulsar  Where were the iron atoms in your blood created?    Inside a high mass star  Black Holes – gravity overwhelms all other forces, contracts forever    As it contracts, gravity gets stronger, meaning the escape velocity gets higher and higher  because it takes more and more to escape.    What’s the cosmic speed limit?  o  Speed of light    Event Horizon:  o  Location where escape speed = the speed of light 
o  Not a real “surface”, but a point of no return 
o  For a 3 M of Sun black hole, event horizon is 9km 
  Very near the event horizon (3x event horizon radius), strange relativistic effects:  o  Time runs slower compared to the rest of the universe 
o  Tidal forces “spaghetiffy” you 
  Everywhere else, just acts like any other object of the same mass 

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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
Name: AY 101 - Midterm 3 Study Guide
Description: Collection of notes and topics since past exam
Uploaded: 11/04/2016
4 Pages 43 Views 34 Unlocks
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