Cassiopeia A (Cas A) is a supernova remnant located about 11,000 light-years from Earth in the constellation Cassiopeia. It spans approximately 10 light-years. X-ray: NASA/CXC/SAO,...
X-ray: NASA/SAO/CXC; Optical: John Stone (Astrobin); Image Processing: NASA/SAO/CXC/L. Frattre, N. Wolk The Cygnus Loop, also known as the Veil Nebula, is a supernova remnant...