Overview
- An international team reports JWST/NIRISS transit spectroscopy of WASP-107b in Nature Astronomy, using multiple observations to track pre-, during-, and post-transit absorption.
- Helium absorption appears before and after transit, revealing flows ahead of and behind the planet that extend to roughly ten times the planet’s radius.
- Beyond helium, spectra show water vapor, carbon monoxide, carbon dioxide, and ammonia in the atmosphere, while methane is notably absent.
- WASP-107b is an extremely low-density “super-puff,” with a radius near Jupiter’s, a mass under one-tenth of Jupiter (about 30 Earth masses), and a tight 5.7-day orbit.
- The team links the inflated, escaping atmosphere and measured composition to a formation-farther-out and inward-migration history, positioning WASP-107b as a benchmark for atmospheric escape studies.