Transcript: The most spectacular type of mass loss occurs in post-main sequence stars undergoing their planetary nebula phase. The name comes because the pale bubbles of gas looked like planets as seen through early small telescopes, but it’s a misnomer. Planetary nebulae have nothing to do with planets. They are the evolved states of stars where the gas is glowing in sheets or spheres around the central stellar core. The gas glows for two reasons: first the large amount of ultraviolet radiation from a hot star at the center and second because the gas is being ejected, and it can be raised in energy in shocks as it hits the interstellar medium. The resulting morphologies can be complex: shells, rings, arcs, or more complicated patterns. The colors are indicative of the chemical elements involved in the gas: the red glow coming from the hydrogen alpha line, and the blue-green glow typically from doubly ionized oxygen. Emission lines of nitrogen, oxygen, carbon, sulfur, chlorine, and iron are routinely seen in planetary nebula indicating the recycling of heavy elements into the interstellar medium from evolved stars.