Figure 18-26: R I V U X G
A Supernova Remnant This composite image shows Cassiopeia A, the remnant of a supernova that occurred about 3000 pc (10,000 ly) from Earth. In the roughly 300 years since the supernova explosion, a shock wave has expanded about 3 pc (10 ly) outward in all directions from the explosion site. The shock wave has warmed interstellar dust to a temperature of about 300 K (Spitzer Space Telescope infrared image in red), and has heated interstellar gases to temperatures that range from 10⁴ K (Hubble Space Telescope visible-light image in yellow) to 10⁷ K (Chandra X-ray Observatory X-ray image in green and blue).

(NASA; JPL-Caltech; and O. Krause, Steward Observatory)