A Two-dimensional Infrared Map of the Extrasolar Planet HD 189733b

We derive the first secondary eclipse map of an exoplanet, HD 189733b, based on Spitzer IRAC 8 μm data. We develop two complementary techniques for deriving the two-dimensional planet intensity: regularized slice mapping and spherical harmonic mapping. Both techniques give similar derived intensity maps for the infrared dayside flux of the planet, while the spherical harmonic method can be extended to include phase variation data which better constrain the map. The longitudinal offset of the dayside hot spot is consistent with that found in prior studies, strengthening the claim of super-rotating winds, and eliminating the possibility of phase variations being caused by stellar variability. The latitude of the hot spot is within 12fdg5 (68% confidence) of the planet's equator, confirming the predictions of general circulation models for hot Jupiters and indicative of a small planet obliquity.