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 micron 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 day-side 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 day-side 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 10.1 deg (68% confidence) of the planet's equator, confirming the predictions of general circulation models for hot Jupiters and indicative of a small planet obliquity.Comment: Modified to reflect erratum regarding a north-south degeneracy in the eclipse mapping (ApJ, 757, L32). Our conclusions are essentially unchange