1. Triple star system consists of two white A stars in a tight orbit, and a more massive, hotter star.
2. More massive star evolves quickly and expands into a red giant.
3. The tight binary pair is engulfed by the red giant.
4. The binary pair "stirs" the red giant's shell, forming a thick disk.
5. Bipolar lobes form above and below the disk to make a planetary nebula. The star's core shrinks down to a white dwarf.