What is a planetary nebula?
A)a disk of gas surrounding a protostar that may form into planets
B)what is left of the planets around a star after a low-mass star has ended its life
C)the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star
D)the molecular cloud from which protostars form
E)the expanding shell of gas that is left when a white dwarf explodes as a supernova

Question

Quizplus · Accepted Answer

A planetary nebula is the glowing shell of gas that is expelled by a low-mass star, such as the Sun, as it approaches the end of its life and begins to evolve into a white dwarf. The expanding shell of gas is no longer gravitationally held to the remnant of the star, and is illuminated by the ultraviolet radiation from the central white dwarf. Planetary nebulae are often among the most beautiful and striking objects in the night sky, with intricate patterns and colors that reflect the complex physics of the gas dynamics and the radiation field.

What Is a Planetary Nebula