6. (15 points)
The star HD 189733 has an effective temperature of 4785 K and a radius of 0.805 Solar radii.
a) Use the depth of the planet’s transit to estimate the radius of HD 189733b, in Jupiter radii.
b) Use the depth of the eclipse of the planet by the host star to estimate the ratio of the flux of the planet HD 189733b to that of the host star HD 189733.
c) HD 189733b is so close-in to its host star that it is expected to be tidally locked. Use the phase curve to estimate the ratio of the dayside flux emitted by the planet to the nightside flux emitted by the planet.
d) This phase curve also noticeably has a phase curve offset, that is, the maximum in planet and star flux does not occur exactly at secondary eclipse. What process that occurs in a planetary atmosphere could cause such a phase curve offset?