(CNN) - Astronomers are getting a closer look at what happens in the heart of an exploding star.
NASA's X-ray NuSTAR telescope collected an incredible image, the first to map radioactive material in a so-called supernova.
The blue color highlights the radioactive material.
Blown-out pieces from a massive exploding star produced this remnant known as Cassiopeia A.
It is located about 11,000 light years away from earth.
Astronomers found radioactive titanium-44, an unstable isotope, was produced in the heart of the exploding star.
The energy from that eventually blew off the star's outer layers.
The full results are published in the journal Nature.
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