What do planetary nebulae have to do with planets?

Answer 1

When William Herschel saw his first one, he called it that because it appeared in his scope as a small, pale green disc, with a similar appearance to Uranus, which he had also recently discovered. It's merely a description of its appearance which stuck. Many discovered since then look nothing like planetary shapes.

Answer 2

Absolutely nothing! A planetary nebula is the name given when a red giant ejects its outer layers at the end of the helium-fusing phase of its lifecycle. (This only happens in stars with an initial mass of less than 8 solar masses. Heavier stars go on to explode as supernova.)
They are called "planetary nebula" because early astronomers thought they looked like planets.

Answer 3

Planetary nebulae got their name from the fact that they appear as roundish pale disks in telescopes, somewhat resembling planets rather than stars. But they have nothing to do with planets -- they are actually *much* bigger than planets, and much further away than any of the planets in our solar system. They are formed from the outer layers of an aging star that are cast off after it has gone through its red giant phase.

Answer 4

As already explained, it was their appearance that led to the Name.
What may not be so obvious, is the fact that, at the time of their discovery, The old Astronomer's Telescopes had such poor optics that details could not be seen.
By comparison, even Amateur Astronomers today, using quite modest equipment can routinely distinguish the details to determine their true nature such as Nebulae, Star clusters, etc.

Adolph

Answer 5

Nothing. Many of them appear as bright discs somewhat resembling planets, hence the name.