Astronomy Week 4 notes
Astronomy Week 4 notes astronomy 113
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This 2 page Class Notes was uploaded by Morgan Owens on Friday February 26, 2016. The Class Notes belongs to astronomy 113 at George Mason University taught by Pesce in Winter 2016. Since its upload, it has received 39 views.
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Date Created: 02/26/16
Astronomy week 4: Star Formation: The interstellar medium: Gas and dust lying between stars, 10% of the mass of our galaxy Hydrogen in the most abundant Others include: H2O, CO, ammonia, hydrocarbons, Amino Acids, Alcohols ISM is found in different states: hot, warm, cold This is debris in between the stars, so typically the ISM blocks the view as we look through the galaxy, the red wavelength light come through the dust. Giant Molecular Clouds: Very cold, dense gas clouds Low energy particles, so they don’t move very far and clump together “heavy” elements (hydrogen 74%, 25% He, 1% other) Very important because they are where stars form, they can ONLY form here. Cloud Collapse: 1. Cold, dense cloud starts to collapse gravitationally One cloud may form many stars (open cluster) The dense core (protostar) collapse quickly as more materials “accretes” onto it 2. After 10^5 years mass builds to ~ 1 M Core heats through the release of gravitational potential energy Radiation pressure stops accretion Protostar – premain sequence star which contracts due to gravity 3. When the core reached T ~ 10^7 K, fusion stars and radiation pressure halts contraction (once this temp is reached fusion starts immediately, and radiate gamma rays) 4. Outer shell of gas/dust is blow off and we have a new star Mass is most important property The stars mass places it on the HR diagram Nebula Hot O and B stars have a lot of ultraviolet radiation and they ionize the surrounding nebula Recombination makes the nebula glow (emission nebula) Because they are made of ionized H, we also call them HII regions (for singly ionized H) Star Clusters: Ionization shell/ Supernovae compress gas leading to star formation Strings of start clusters of increasing age in large star forming regions By plotting stars in clusters, can determine age Extrasolar Planetary Systems: Newly formed stars everywhere with gas/dust clouds and disks Planets form everywhere Hundreds of extrasolar planets found, of all sorts
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