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Astronomy Week 3 notes + Exam 1 hints

by: Morgan Owens

Astronomy Week 3 notes + Exam 1 hints astronomy 113

Marketplace > George Mason University > astronomy 113 > Astronomy Week 3 notes Exam 1 hints
Morgan Owens
GPA 3.5

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These notes cover what was covered in class for the third week. Everything here will be on the exam so start studying! Exam study guide coming soon!
Intro to Astronomy
Class Notes
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This 3 page Class Notes was uploaded by Morgan Owens on Wednesday February 10, 2016. The Class Notes belongs to astronomy 113 at George Mason University taught by Pesce in Winter 2016. Since its upload, it has received 752 views.


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Date Created: 02/10/16
Astronomy week 3: The Sun The nearest star­ easiest to study­ we can use it as a model The atmosphere of the sun is called the Photosphere (level 1) 1. ­ Deepest layer we can see visibly , where they visible light photons come from  ­ Low density ­ Perfect black body at 5800 K ­ We can’t see below the photosphere ­ Important features: granulation (grainy looking) & limb darkening (bright in the middle  and get darker at the edges­ #1 evidence that proves that the sun is made of gas) 2. Level 2: chromosphere:  ­ layer of less dense gas above the photosphere ­ about 500 km think ­ features: spicules­ which are spikes or jets of gas 3. Corona Level 3: upper most layer of atmosphere; it extends to millions of km ­ Very low density ­ Can only been see during eclipses ­ 2 million degrees   ­ Heated by magnetic fields ­ Iodized particles in the corona have so much energy that they float away from the sun,  resulting in the sun losing mass, at a rate of 2 million tons per second = this is called the  Solar Wind Sunspots: cooler regions on the surface (where magnetic fields exit and enter the Sun) ­ Follow a 11 year cycle ­ 10,000 km (earth sized) ­ Appear black on the surface because they are cooler which makes them not as bright ­ Can determine sun’s rotation rate ­ Differential rotation­ equator rotates more rapidly than the poles (E=once every 25 days,  poles = once every 35 days) – proves that the sun is not a solid body Solar Flares­ eruptions of charged particles and radiation The Solar Interior th The energy source­ in the 18  century we didn’t know how old the earth was but people  were wondering what powers the sun. In the late 19  century, Kelvin realizes that the sun  has to be much older then he original prediction.  In the core on the sun we have Thermonuclear Reactions: ­ E=mc^2 ­ C= speed of light ­ M=mass ­ E = energy  Fusion in Core­ because protons stick together. Fundamentally what is happening is that protons  are sticking together.  4 Hydrogen (smashed together) = 1 Helium + energy + neutrinos For this reaction: E=4 x 10^­12 (enough energy to light a 10W light bulb for 5 x 10 ^­12  seconds) This means that the sun is converting 600 million metric tons per second of Hydrogen into  Helium.  Fusion Neutrinos: Nearly massless subatomic particles, produced in huge quantities during fusion and supernovae.  ­ Important for cosmological reasons and understanding of nuclear fusion ­ Billions of them pass through every square centimeter all the time ­ Weakly interacting: can pass through 1 light year of lead without interaction with a lead  atom. Even though there are 100 million of them going through our body every second,  in one year 1 neutrino will react with 1 water molecule.  ­ Can be detected Important *Hydrostatic Equilibrium: balance of force of gravity, which tries to squeeze the  Sun, and a radiative pressure from fusion, which tries to blow apart Sun Radiative transport: Energy transported outward by photons ­ High P, High T create high E photons (γ­ rays) ­ But high P keeps them in, leading to a random walk.  ­ Random Walk­ photons collide, lose E, eventually fly free from photosphere as visible  photons.  Transport of Energy: Radiative= photons +convection “Random walk”: γ­ray to visible (infrared) At the end of class Pesce stated that students should know the HR diagram very well in order  to do well in the exam. He also said it is important to understand luminosity, absolute  magnitude and what the main sequence is. 


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