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

TL;DR

This paper presents the first infrared map of an exoplanet's day side, derived from Spitzer data, revealing hot spot location and supporting models of atmospheric circulation.

Contribution

It introduces two novel techniques for creating two-dimensional infrared maps of exoplanets from observational data.

Findings

The hot spot is offset eastward, consistent with super-rotating winds.

The hot spot's latitude is near the equator, supporting circulation model predictions.

The methods produce similar maps, validating their effectiveness.

Abstract

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.