Great Observatories portrait of Cas A This stunning portrait of supernova remnant Cassiopeia A (Cas A) is made from images taken by three of NASA's Great Observatories. Warm dust seen by the Spitzer Space Telescope is red; visible filaments of hot gas seen by the Hubble Space Telescope are yellow; and extremely hot, X-ray-emitting gas seen by the Chandra X-ray Observatory is shown in green and blue. Located 11,000 light-years away in the northern constellation Cassiopeia, Cas A is the remnant of a once massive star that died in a violent explosion 325 years ago. It consists of a central remnant called a neutron star and a surrounding shell of material blasted off the star as it died. Cas A, site of our galaxy's most recent supernova, is one of the most studied objects in the sky.
NASA / JPL-Caltech / O. Krause, Steward Observatory