In 2026, an international team led by Dr Brandt Gaches developed a high‑resolution 3D model showing how uneven density in the Orion Bar creates shadows that alter gas‑phase chemistry and affect infrared emission from the James Webb Space Telescope (JWST).
Earlier studies treated the Orion Bar as a series of one‑dimensional layers, but the new approach captures its full three‑dimensional structure at high resolution. Dr Brandt Gaches leads the Emmy Noether Research Group on molecular astrophysics at the University of Duisburg‑Essen.
Dr Zhengping Zhu of Zhejiang Lab created a highly efficient ray‑tracing algorithm for the model. It enables researchers to model the Orion Bar in three dimensions at a spatial resolution higher than that of earlier models.
The model tracks how molecular hydrogen (H₂), a molecule made of two hydrogen atoms, behaves under the intense stellar radiation that fills the three‑dimensional gas distribution. Simulations reveal where atomic hydrogen (single hydrogen atoms) converts to molecular hydrogen and where ionized carbon (carbon that has lost an electron) recombines within the cloud.
Dense regions block incoming radiation, creating shadows and shielded pockets where chemistry develops differently. Gaches states that the three‑dimensional structure creates shadows that shield parts of the cloud from the intense stellar radiation. He says this altered chemistry leaves a clear signature observable from infrared to radio wavelengths. The uneven structure produces arcs and filaments that match the structures observed by JWST.
The model enables researchers to generate synthetic JWST images for direct comparison with actual telescope data. This capability allows scientists to study how the three‑dimensional shape of a stellar nursery influences its chemistry in ways that one‑dimensional models cannot.
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