Nebulae Composition Astrophysics Universe Formation Nebulae Composition Questions What percent of stars become planetary nebulas? How is a planetary nebula formed? How are planetary nebulae detected? How did planetary nebulae get their name? How do planetary nebulae differ from one another? How does gas for a nebulae constantly keep getting replenished? What are three examples of how the nebular theory explains some observed features of the present-day solar system? Universe Formation View all chapters Planet Composition Galaxy Composition Nebulae Composition Big Bang and Universe Evolution Prev Next