Planetary Nebulae
Planetary nebulae are glowing gas shells ejected by dying stars, illuminated by a hot central white dwarf. Despite their name, they aren’t planets; early astronomers mistook their round, disk-like shape for planets in mini telescopes.
Planetary nebulae are glowing, ionized shells of gas and dust ejected from a dying star in its late red-giant phase, illuminated by the intense ultraviolet radiation of its hot central white-dwarf remnant. Though named for their disk-like appearance resembling planets in early telescopes, they are not related to actual planets. They represent a brief, visible stage in stellar evolution before the star fades into a black dwarf.
What this means in real life
When a middle-aged star like our Sun exhausts its fuel, it puffs off its outer atmosphere into space. If you observe this expanding gas cloud through a telescope, you see a glowing ring or bubble—that's a planetary nebula, beautiful but marking the star's death.
What it isn’t
They are not related to planets or planetary systems. The misleading name comes from 18th-century astronomers who saw their round, disc-like appearance and mistakenly thought they were planets; modern observations revealed they are actually stellar remnants.
Commonly misused online
Social media often calls any colorful space image a 'planetary nebula' for aesthetic appeal, even when it's a different object like a supernova remnant or emission nebula. The term gets stretched to mean 'any pretty glowing cloud in space.'