Planetary Nebula is a shell of gas ejected by a Low Mass Star late in its evolutionary lifetime. Planetary Nebulas are seen as glowing gas rings around a central star.
Planetary Nebula shell has about one-fourth solar mass of glowing gas and several solar masses of cooler nonluminous gas around it.
hells are typically one quarter of a light year in diameter and have an expansion rate of twenty kilometers per second. The shells eventually grow so big that they diffuse and mingle with the other interstellar elements. When this happens the core of the star is left behind as a White Dwarf.
