A complex structure of escaping helium spanning more than half the orbit of the ultra-hot Jupiter WASP-121 b.

ABSTRACT: Atmospheric escape of close-in exoplanets, driven by stellar irradiation, influences their evolution, composition, and atmospheric dynamics. The near-infrared metastable helium triplet (10833 Å) has become a key probe of this process, enabling mass loss rate measurements for dozens of exoplanets. Only a few studies, however, have detected absorption beyond transit, supporting the presence of hydrodynamic outflows. None have yet precisely identified the physical extent of the out-of-transit signal, either due to non-continuous or short-duration observations. This strongly limits our ability to measure accurate mass-loss rates and to understand how the stellar environment shapes outflows. Here we present the continuous, full-orbit helium phase-curve observation of an exoplanet: the ultra-hot

SUBMITTER: Allart R 

PROVIDER: S-EPMC12686059 | biostudies-literature | 2025 Dec

REPOSITORIES: biostudies-literature