Question

What is a "planetary nebula"?

It is the disk of gas around a young star.
It is the cloud from which protostars form.
It is a shell of gas ejected from a star late in its life.
It is what is left when a white dwarf star explodes as a supernova.

Answer 1

A planetary nebula is a shell of gas ejected from a star late in its life. It is formed when a low-mass star expels its outer layers of gas into space.

Step-by-step explanation:

A planetary nebula refers to a shell of gas ejected from a star late in its life. It is formed when a low-mass star, nearing the end of its life, expels its outer layers of gas into space, creating a glowing shell of gas. These nebulae glow due to the ultraviolet energy emitted by the central star.