1 May 2025

Using NASA’s James Webb Space Telescope, astronomers uncovered a mysterious feature within the remnant, nicknamed the “Green Monster,” alongside a puzzling network of ejecta filaments forming a web of oxygen-rich material. When combined with X-rays from NASA’s Chandra X-ray Observatory, the data helped astronomers shed light on the origin of the Green Monster and revealed new insights into the explosion that created Cas A about 340 years ago, from Earth’s perspective.

Like with the Cygnus Loop, Chandra has provided a 3-dimensional (3D) printable model that can be used to explore the end stage of a star’s life. These 3D models are based on state-of-the-art theoretical models, computational algorithms, and observations from space-based telescopes like Chandra that give us accurate pictures of these cosmic objects and how they evolve over time.

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Cassiopeia A (Cas A) is a supernova remnant located about 11,000 light-years from Earth in the constellation Cassiopeia. It spans approximately 10 light-years.