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JWST Detects First Extragalactic Methyl Radical in Carbon‑Rich, Dust‑Buried Galaxy

Spectroscopy indicates cosmic rays are breaking larger carbon materials into small organics inside the obscured nucleus.

Overview

  • The peer‑reviewed study of IRAS 07251–0248 appears in Nature Astronomy, led by CAB (CSIC‑INTA) with University of Oxford collaborators.
  • JWST combined NIRSpec and MIRI data across 3–28 microns to identify gas‑phase chemistry alongside signatures from ices and carbon‑rich dust.
  • The spectra reveal abundant small hydrocarbons including benzene, methane, acetylene, diacetylene, and triacetylene, plus the first confirmed methyl radical beyond the Milky Way.
  • The nucleus also hosts substantial water ice and carbonaceous grains, allowing the team to assess how carbon partitions between solids and gas.
  • The authors propose cosmic‑ray fragmentation of PAHs and carbon grains as the source of the molecules, supported by a hydrocarbon–cosmic‑ray ionization correlation and abundances that exceed current models.