ow mass stars, like every other star, begin life as a part of an Interstellar Cloud. As the cloud picks up stellar dust and other space junk the increasing gravity causes the cloud to collapse. As it collapses the cloud becomes smaller and hotter.

fter a few million years the low mass star begins to fuse helium into hydrogen. When this happens the collapse is ended because the fusion raises the pressure inside the star. During this period the star is commonly referred to as a Protostar.

hen the star burns about 90% of the hydrogen in its core, the core will shrink, burning the hydrogen even more quickly, generating more energy. As this energy flows outward it pushes out the stars outer layers. When the outer layers cool away from the core they turn red, at this time the star is called a Red Giant.

rom there the star transforms into a Yellow Giant once it cools enough to fuse helium again. During this stage the star glows. After the star uses up the helium at its core it becomes a Red Giant, only much larger than the first time.

he high luminosity in the larger Red Giant is what causes the star's death. The radiation streaming outward drives the gas into space, stripping the star to its core. The gas that has been ejected forms a shell around the star which will eventually disperse. This shell is called a Planetary Nebula, which is quite an inappropriate name as the phenomenon has nothing to to with planets. The Planetary Nebula got its name in the early days of astronomy when poor telescopes made the glowing shell appear to be a planet.