Astr 202

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Astr 202
2013-10-16 20:22:56

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  1. wavelength
    is the distance between adjacent pearks of the electric (and magnetic) field
  2. frequency
    is the number of times each second that the electric (and magnetic) field vibrates up and down (or side to side) at any point

    (all light travels with speed c=300,000 km/s
  3. Typical units

    Wavelength: meter
    Frequency: Hz (beat/second)
    • shorter wavelength=Higher frequency
    • longer wavelength= lower frequency

    (ex: rope in class)
  4. Electron can only be in specific states in the atom.Each state has different energy. The lowest energystate is the ground state.
  5. composition: absorption/emission lines
    Temperature/size: continuun emission
  6. where start come from
    • in the milky galaxy stars form an avg 1 star/year
    • dust/gas clouds can collapse under their own gravity
    • a thick dick forms that feeds the protostar in its center
    • during the collapse, the center get hotter and hotter
  7. stars
    most most massive stars live only <10 myr, stars like ours live -10 Gyr and lowest mass stars live more than a trillion years
  8. why stars die
    when there are not enough light nuclei in the core, the balance between the pressure(from energy production) and gravity is disturbed the star undergoes rapid evolution, trying to regain its balance, gaining energy from fusing heavier nuclei and from fusion outside its core. in the final stages of evolution stars will often eject most of their mass
  9. cont.
    • as stars run out of hydrogen in their cores,they can also fuse heavier elements. (fusing 3 He nuclei= 1 Carbon nucleus+energy)
    • in more massive stars, futher elements can be generated: carbon nuclei can be fused to form oxygen and silicon oxygen nuclei can be fused to form neon and sulfur, up to iron
    • Elements heaver than iron form in supernova explosions
    • elements ejected from the stars will form dust and gas particles and become part of a next generation of stars!