It appears to be a fairly common planetary naming scheme in science fiction: Take the common name (or its bayer designation) of star and append the planetary ordinal in the form of a Roman or Arabic numeral.

## Examples

* [Earth](https://en.wikipedia.org/wiki/Earth) becomes _Sol Ⅲ_
* The tenth planet of [Pollux](https://en.wikipedia.org/wiki/Pollux_(star))
 becomes [_Pollux Ⅹ_](https://memory-alpha.fandom.com/wiki/Pollux_IV)
* The forth Planet of [Beta Hydri](https://en.wikipedia.org/wiki/Beta_Hydri) becomes [_Beta Hydri Ⅳ_](https://en.wikipedia.org/wiki/The_Man_in_the_Maze_(novel))

## It's not based in reality

I asked an astronomer and he assured me, no astronomer ever proposed such a naming system.

Real exoplanets today are named using [an entirely different naming scheme.](https://en.wikipedia.org/wiki/Exoplanet_naming_convention#Circumbinary_planets_and_2010_proposal)

## Who came up with it?

It is very common in _Star Trek_, but it exitsted in earlier science fiction novels and short stories. What is the earliest occurrence of this naming scheme? When was it first described? When was it first _implied_?