Unit 5 Astrophysics

  • Created by: megan
  • Created on: 24-03-13 17:14
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  • Astrophysics and Cosmology
    • The attraction of the stars
      • Every particle with mass attracts every other particle with mass.
      • The big bang spread tiny particles across space, the particles move towards each other and clump together
        • This effect is more pronounced for particles nearer to each other.
      • a particle that has a mass will feel a force when it is in a gravitational field
        • The force that a body will feel is the strength of the gravitational field multiplied by the amount of mass
          • f=mg=ma.
      • a massie particle will generate a radial gravitational field around itself
        • Gravity is always attractive
      • The gravitational force between two masses which are separated by a distance is F= Gm1m2/r^2
        • G Is the gravitational constant = 6.67x10^-11
    • Gravitation field strength
      • The strength of the field decreases with increasing distance from the mass causing it.
      • The field strength is independent of the object being acted upon.
      • g= -GM/r^2
    • Electric and gravitational fields
      • They are similar because they are both types of field that are radial from a point.
      • They differ because gravitational field is always attractive and an electric field is not. Electric fields are also stronger than gravitational fields
    • Stella Properties
      • The only information we receive from the stars is the electromagnetic radiation from them
        • This tells us their temperature, chemical composition, speed of movement, age and size.
    • The stefan botlzmann law
      • Luminosity is the precise measure used to classify the brightness of stars.
        • Is is the rate at which energy of all types is radiated by an object in all directions
        • Luminosity depends on size and temperature.
      • A perfect radiator is a black body and will give off energy across the entire electromagnetic spectrum
      • The stefan boltzmann law tells us that the power output from a black body is proportional to its surface area and the forth power of its temperature.
        • L= oT^4 4Pi r^2
          • o= 5.67x10^-8
    • Wiens law
      • To calculate luminosity we need to know the temperature of the star.
      • As the temperature increases, a star emits more energy.
        • The wavelength of the peak wavelength gets shorted as temperature rises
      • Max Wavelength x Temperature = 2.89x 10^-3


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