A planetary nebula in the constellation Centaurus. At the center of the nebula are two stars: a white dwarf and a red giant, each with a mass roughly equal to that of the Sun. The red giant star turns out to be a Mira variable, a pulsating star that is dumping material into an accretion disk surrounding the white dwarf. It is thought that when enough mass falls onto the white dwarf, a thermonuclear explosion occurs creating another expanding hourglass-shaped nebula. The photograph shown here was taken with the WFPC2 instrument onboard the Hubble Space Telescope. The hourglasses from the two most recent explosions are visible with the last one highlighted in the inset.
