What is a planetary nebula?
A)the expelled outer envelope of a medium mass star
B)a cloud of hot gas produced by a supernova explosion
C)a nebula within which planets are forming
D)a cloud of hot gas surrounding a planet

Question

Quizplus · Accepted Answer

A planetary nebula is the ejected outer envelope of a medium mass star. As the star runs out of fuel, it undergoes a series of processes which eventually lead to the ejection of its outer layers, forming a new bubble-like structure. This structure is then ionized by the remaining hot core of the star, producing a glowing nebula. The term "planetary" is actually a misnomer, as these objects have nothing to do with planets. They were originally named by William Herschel, who thought they resembled planetary disks when viewed through a telescope.

What Is a Planetary Nebula