This new view of the historical supernova remnant Cassiopeia A, located 11,000 light-years away, was taken by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. Blue indicates the highest energy X-ray light, where NuSTAR has made the first resolved image ever of this source. Red and green show the lower end of NuSTAR's energy range, which overlaps with NASA's high-resolution Chandra X-ray Observatory.
NuSTAR - News Detail
http://www.nustar.caltech.edu/news/99/62/NASA-s-NuSTAR-Catches-Black-Holes-in-Galaxy-Web/d,news-detail