Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy

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Science  14 Nov 2014:
Vol. 346, Issue 6211, pp. 838-841
DOI: 10.1126/science.1256758

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Exoplanets that orbit close to their host stars are much more highly irradiated than their solar system counterparts. Understanding the thermal structures and appearances of these planets requires investigating how their atmospheres respond to such extreme stellar forcing. We present spectroscopic thermal emission measurements as a function of orbital phase (“phase-curve observations”) for the highly irradiated exoplanet WASP-43b spanning three full planet rotations using the Hubble Space Telescope. With these data, we construct a map of the planet’s atmospheric thermal structure, from which we find large day-night temperature variations at all measured altitudes and a monotonically decreasing temperature with pressure at all longitudes. We also derive a Bond albedo of Embedded Image and an altitude dependence in the hot-spot offset relative to the substellar point.

Sunny side hot for tidally locked world

Most planets in our solar system spread their heat evenly across their surfaces in the course of a day. They accomplish this with relatively fast rotations and a generous distance from the Sun. Some exoplanets, however, aren't so well balanced. Stevenson et al. show that planets like the Jupiter-sized WASP-43b whirl closely around their star in less than 24 hours, which leaves them tidally locked with little chance for heat redistribution.

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