Unraveling the atmosphere of WASP-103b from its JWST/NIRSPec-Prism phasecurve

Ultra-hot Jupiters exhibit extreme day-to-night temperature contrasts exceeding 1000 K, driven by the competing effects of strong atmospheric winds, short radiative timescales, magnetic drag, and H₂ dissociation and recombination. Spectroscopic phase curves provide a uniquely powerful tool to probe these processes by mapping longitudinal temperature distributions and constraining planetary energy budgets across a range of atmospheric pressures.

We present results from a full-orbit phase-curve observation of the iconic ultra-hot Jupiter WASP-103b, obtained with JWST/NIRSpec-PRISM optical to near-infrared wavelengths in a single continuous visit. This observation provides an unprecedented view of a strongly tidally influenced exoplanet, enabling simultaneous constraints on atmospheric structure, dynamics, and composition as a function of orbital phase.

From the phase-resolved spectra, we measure wavelength-dependent hotspot offsets and quantify the planet’s heat redistribution efficiency, revealing the combined impact of extreme irradiation and short radiative timescales on the longitudinal temperature gradients. We will present the planet's emission spectra, probing the dayside and nightside atmospheric chemistry, and also the transmission spectrum constraining the terminator composition. Together, the data tests the predictions of chemical equilibrium and thermal structure models for ultra-hot Jupiters, including the survival of key molecular species at different longitudes.

Beyond atmospheric characterization, the phase-curve morphology of WASP-103b carries signatures of tidal deformation, providing important context for understanding how intense star–planet interactions shape both atmospheric dynamics and planetary evolution. The talk will discuss the power of JWST full-orbit spectroscopy to connect atmospheric circulation, chemistry, and tidal physics in extreme exoplanets and establish WASP-103b as a benchmark target for studies at the intersection of exoplanet atmospheres and interiors.