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 The average albedo of the moon is only 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

16. Occulters