Overview
- XRISM’s Resolve instrument captured high-resolution X-ray spectra of Cassiopeia A in December 2023 that clearly reveal chlorine and potassium.
- The measured abundances of both elements exceed standard supernova nucleosynthesis predictions by large margins.
- Researchers propose that strong internal mixing in massive stars, potentially from rapid rotation, binary interaction or shell-merger events, boosted odd-Z element production.
- The elements are concentrated in the remnant’s southeast and northern regions, a lopsided pattern that points to asymmetries in the progenitor star or explosion.
- The peer-reviewed findings were published Dec. 4 in Nature Astronomy, and the team plans further XRISM surveys to determine whether Cas A is typical.