Figure 20-17:
SN 1987A and Its “Three-Ring Circus” (a) This true-color view from the Hubble Space Telescope shows three bright rings around SN 1987A. (b) This drawing shows the probable origin of the rings. A wind from the progenitor star, shown in Figure 20-16a, formed an hourglass-shaped shell surrounding the star. (Compare with Figure 20-8.) Ultraviolet light from the supernova explosion ionized ring-shaped regions in the shell, causing them to glow.
SN 1987A and Its “Three-Ring Circus” (a) This true-color view from the Hubble Space Telescope shows three bright rings around SN 1987A. (b) This drawing shows the probable origin of the rings. A wind from the progenitor star, shown in Figure 20-16a, formed an hourglass-shaped shell surrounding the star. (Compare with Figure 20-8.) Ultraviolet light from the supernova explosion ionized ring-shaped regions in the shell, causing them to glow.
(Robert Kirshner and Peter Challis, Harvard-Smithsonian Center for Astrophysics; STScI)