ASTR 1220 Final Exam

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ASTR 1220 Final Exam
2014-05-07 20:54:11
astronomy final exam

Terms for the ASTR 1220 Final Exam
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  1. rate of energy flow
  2. watt
    measure of energy flow (power) equal to 1 joule/s
  3. emission
    when a source produces light
  4. absorption
    when light is absorbed by matter (i.e. your hand absorbing light from a light bulb)
  5. transmission
    when light passes through a form of matter
  6. reflection/scattering
    when light bounces off something in the same general direction (reflection) or multiple random directions (scattering)
  7. measure of light frequency
    Hertz (Hz), cycles per second
  8. blackbody
    a perfect body that completely absorbs every kind of electromagnetic radiation and reradiates the energy as quickly as it absorbs it
  9. The 3 properties of blackbodies are:
    • 1. Every blackbody emits some radiation at every wavelength
    • 2. A hot blackbody emits more radiation at every wavelength than a cool one
    • 3. The peak wavelength of the radiation from a hot body is at a shorter wavelength than that for a cool body
  10. The most common elements in the universe are:
    • 75% H
    • 24% He
    • 1% other
  11. continuous spectrum
    a spectrum from an source like an ordinary light bulb that spans a broad range of wavelengths without interruption
  12. emission line spectrum
    the spectrum obtained from a thin, low-density cloud of gas that consists of thin emission lines that depend on the gas' composition
  13. absorption spectrum
    a continuous spectrum that is missing several colors that have been absorbed by a cloud of gas
  14. Stefan-Boltzmann Law
    • The total energy emitted per square meter of a blackbody is given by 
    • Therefore, temperature strongly affects the amount of energy emitted
  15. Wien's Law
    Hotter objects emit photons with a higher average energy (shorter wavelength), given by 
  16. A light source moving towards the observer causes
    blueshift (shorter wavelengths)
  17. A light source moving away from the observer causes
    redshift (longer wavelengths)
  18. luminosity
    the power output of a star, or other blackbody
  19. A nuclear fusion reaction of 1 kg of hydrogen produces
    992.9 kg of helium, ~7.1 kg are converted into energy
  20. ___% of the Sun's energy is generated in the _____ of the Sun
    94% of the Sun's energy is generated in the inner 20% of the Sun
  21. The closest star to our Sun is
    Alpha Centauri (4.4 LY or 1.3 parsecs)
  22. Brightness is given by
  23. Kepler's First Law
    Planets orbit stars in elliptical orbits, with the star at one of the foci of the ellipse
  24. Kepler's Second Law
    The straight line joining a planet and the Sun sweeps out equal areas in space in equal intervals of time
  25. Kepler's Third Law
    • The squares of a planet's period of revolution is directly proportional to the cube of its semimajor axis.
    • , where d = distance (AU), p=period (years)
  26. The lifetime of our Sun is
    10 billion years
  27. The lowest mass a protostar can have before it becomes a brown dwarf is
    0.08 MSun
  28. Stars with a mass of _______ will leave behind planetary nebulae
    <8 MSun
  29. Stars whose core has a mass of _______ will form a white dwarf.
    <1.4 MSun
  30. Stars with a mass of ______ will die in a supernova.
  31. Stars whose cores have a mass of _______ will form neutron stars.
    1.4MSun < MCore < 3MSun
  32. Stars with a mass of ______ who have cores with a mass greater than _______ will form black holes.
    MStar > 20MSun, MCore > 3MSun
  33. The definition of a black hole is...
    an object whose escape velocity exceeds the speed of light.
  34. Escape velocity is
    • the velocity required for an object to break free from a body's gravity.
  35. Schwarzchild Radius
    The radius at which an object of a certain mass becomes a black hole.
  36. pulsar
    A highly dense, rapidly spinning object, most likely a neutron star, that emits radio signal pulses at very regular intervals.
  37. Hubble Law
    Used to calculate the distance to objects based on how rapidly they appear to be moving away from us.
  38. The universe is currently accepted to be _______ years old.
    13.7 billion years