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5d ago

JWST Finds Heavy, Water-Rich Atmosphere on Mini-Neptune in Rare Hot-Jupiter System

The molecule-rich air points to a far-out birth followed by slow inward migration.

Image
An artist's impression of the TOI-1130 system, where a mini-Neptune and a hot Jupiter, a colossal gas giant, orbit their star together in one of the rarest planetary pairings ever discovered. (Image: Jose-Luis Olivares, MIT)
image: ©JulPo | iStock

Overview

  • The MIT-led team reported Thursday in Astrophysical Journal Letters that JWST measured water vapor, carbon dioxide, sulfur dioxide and traces of methane in TOI-1130b’s atmosphere.
  • The mix signals a high mean molecular weight atmosphere that is hard to build near a star, which points to formation beyond the system’s frost line where water freezes into ice.
  • The findings indicate the mini-Neptune and its hot-Jupiter neighbor likely migrated inward together and now orbit in a 4- and 8-day mean-motion resonance.
  • Observers had to model the planets’ tug-of-war to predict exact transit times, since the resonance shifts when each world crosses the star and when JWST can take spectra.
  • The TOI-1130 system, about 190 light-years away and first flagged by NASA’s TESS in 2020, is the first case where scientists have measured a mini-Neptune’s atmosphere inside a hot Jupiter’s orbit.