Final answer:
A planetary nebula is a region where jets of gas from young stars impact and heat the gas surrounding the young star.
Step-by-step explanation:
A planetary nebula is a region where jets of gas from young stars impact and heat the gas surrounding the young star. As low-mass stars near the end of their lives, they eject a shell of gas that expands away from the star. This shell of gas, known as a planetary nebula, glows because of the ultraviolet energy emitted by the central star.