XRISM Finds Chlorine, Potassium in Cas A

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XRISM Finds Chlorine, Potassium in Cas A

Jeanette Kazmierczak

Monika Luabeya

Dec 08, 2025 Image Article

This composite image of the Cassiopeia A (or Cas A) supernova remnant, released Jan. 8, 2024, contains X-rays from Chandra (blue), infrared data from Webb (red, green, blue), and optical data from Hubble (red and white). A study by the XRISM (X-ray Imaging and Spectroscopy Mission) spacecraft has made the first-ever X-ray detections of chlorine and potassium in the wreckage. X-ray: NASA/CXC/SAO; Optical: NASA/ESA/STScI; IR: NASA/ESA/CSA/STScI/Milisavljevic et al., NASA/JPL/CalTech; Image Processing: NASA/CXC/SAO/J. Schmidt and K. Arcand

The Cassiopeia A supernova remnant glows in X-ray, visible, and infrared light in this Jan. 8, 2024, image that combines data from NASA’s Chandra X-ray Observatory and Hubble, Webb, and Spitzer space telescopes. A study by the XRISM (X-ray Imaging and Spectroscopy Mission) spacecraft has made the first-ever X-ray detections of chlorine and potassium from the wreckage; a paper about the result was published Dec. 4, 2025, in Nature Astronomy.

Read more about this discovery.

Image credit: X-ray: NASA/CXC/SAO; Optical: NASA/ESA/STScI; IR: NASA/ESA/CSA/STScI/Milisavljevic et al., NASA/JPL/CalTech; Image Processing: NASA/CXC/SAO/J. Schmidt and K. Arcand