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Imaging Planets

Imaging Planets. FRS 120 Lecture 4. Light as a Wave. Light as a Particle. Light comes in individual “quanta” of energy. How many photons does a 100 W light bulb emit in a second? About 3e20 photons/s. Thermal Radiation.

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Imaging Planets

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  1. Imaging Planets FRS 120 Lecture 4

  2. Light as a Wave

  3. Light as a Particle Light comes in individual “quanta” of energy. How many photons does a 100 W light bulb emit in a second? About 3e20 photons/s

  4. Thermal Radiation • The radiation from most bodies can be approximated as “black body radiation” with a characteristic temperature. • The luminosity emitted by a black body scales as its surface area:

  5. Conservation of energy How many photons does the puppy see from a 100 W bulb at a distance of 100 m?

  6. Scattered light from a planet Energy/time striking planet

  7. Albedo Albedo is the fraction of light scattered off of a planet. Albedo varies from 0.04 for fresh asphalt to 0.8 for freshly fallen snow. The average albedo of the earth is 0.3. The average albedo of the moon is only 0.12. The moon absorbs 88% of the light that strikes its surface. Luminosity of Planet = (albedo) (Energy/time hitting planet) What is the ratio of the luminosity of the earth in reflected light to the luminosity of the Sun?

  8. aFin r Fin Heating rate of planet = Cooling rate of planet = Heating = Cooling (Thermal Equilibrium)

  9. Blue stars are hotter than red stars Visible Infrared

  10. Resolving Power of a Telescope

  11. Telescope Optics

  12. The Diffraction Problem (Visible) Wavelength (l) Focal plane 1 Diameter (D) Entrance Pupil 1e-10 Size of Image is a function of Telescope Size and Wavelength

  13. Coronagraphs Space-based Coronagraph SOHO image of the solar corona

  14. HR 8799

  15. Occulters

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