This nearby SNR has been studied extensively and it offers a great opportunity to study the evolution of this kind of sources, and also verify explosion and evolution models of supernovae.
A few years ago, scientists detected phosphorus in Cas A, which confirmed that this element is produced in supernovae. Note that in a supernova remnant the phosphorus iron ratio could be 100 higher than in the Milky Way on average.
A few days ago astronomers announced that titanium was also detected in Cas A, using X-ray data from Chandra X-ray Observatory. Thus, a crucial element has been added in our understanding of elements synthesis and supernova. According to theoretical models, titanium is believed to be formed in bubbles that drive the explosions of massive stars. Such bubbles propagate through the star and they drive the SNR rim.
Titanium was detected in structures pointing outwards that coincide together with iron and chromium debris. The titanium emission detected by Chandra comes from a stable isotope of titanium (i.e., it does not decay into a lighter element).
Image: Composite image from Cas A, created using X-ray data from Chandra and NuSTAR, together with optical data from Hubble Space Telescope. X-ray emission is due to certain elements, thus orange is due to iron, purple due to oxygen, green comes from the amount of silicon compared to magnesium, while light blue color is due to titanium. Finally, the optical emission here is shown in yellow.
Image Credit: Chandra: NASA/CXC/RIKEN/T. Sato et al.; NuSTAR: NASA/NuSTAR; Hubble: NASA/STScI
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