Such observations are one of the primary goals of NASA's NuSTAR mission, launched in June 2012 to measure high-energy X-ray emissions from exploding stars, they said.
While the well-known supernova remnant known as Cassiopeia A has been photographed by many optical, infrared and X-ray telescopes in the past, NuSTAR has produced the first map of high-energy X-ray emissions from material created in the actual core of the exploding star that produced the remnant, astronomers said.
The material is the radioactive isotope titanium-44, which was produced in the star's core as it collapsed to a neutron star or black hole.
"This has been a holy grail observation for high energy astrophysics for decades," said study co-author and NuSTAR investigator Steven Boggs of the University of California, Berkeley.
"For the first time we are able to image the radioactive emission in a supernova remnant, which lets us probe the fundamental physics of the nuclear explosion at the heart of the supernova like we have never been able to do before."
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