Abell 78 is a planetary nebula located in the constellation of Cygnus at a distance of about 5,000 light years. It has a fainter halo consisting mostly hydrogen, an inner elliptical ring that is mostly made of helium and some inner knots that surround the central star and are extremely depleted in hydrogen. These inner knots were created by a very late thermal pulse, a re-ignition of thermonuclear activity in the helium shell of the star observed after the star left the asymptotic giant branch and is accompanied by strong stellar winds.[1] [2]
The central star of the planetary nebula has a spectral type of [WC5], similar to that of a carbon-rich Wolf–Rayet star.[3] The spectrum of the inner knots is indicative of the presence of a binary system.[1]