Here’s the thing. While playing Final Fantasy 7 literally in the first mission I encountered a dilemma. When Barret was explaining what Mako reactor does he said 「この星は魔晄（まこう）エネルギーに満ちている。住民はその魔晄エネルギーを使って日々生活している」
In English translation 星 means Planet. In retranslated English version it also means Planet, even though there are a lot of words in Japanese that 100% means a planet for example: 惑星, 遊星 or 母星.
I believe that when you read 星 the first thing that comes to mind is a star, not the planet. Also 魔晄エネルギー has 晄 kanji which means clear/bright. And it makes sense that some kind of bright demonic energy comes from a star, not from a planet. But those two English versions confuse me and I don’t know what to think. Can anyone help please? =)
Edit: Thanks for the answers it all make sense now. I’m also started to question credibility every single dictionary I used before xD
In the broadest usage, 星 is any visible (light emitting or reflecting) object in space (and presumably your own planet in a science fiction story would qualify as such a thing). Comets and moons can be included, but not Earth’s moon or the Sun or Earth. It’s not a strict scientific term. The proper term to specify a star is 恒星 (こうせい) and to specify a planet, 惑星 (わくせい). You’ll notice that 星 is used in both.
As for why the Japanese writers chose 星 when 惑星 exists, since 星 is not a strict scientific term, maybe it’s just what they think Barret would be more likely to use.
The origin of the word “planet” in English is not that different in terms of scientific unhelpfulness. It comes from a Greek word meaning “wanderer,” as in “stars that wander in the sky.”
I don’t think it even has to be light-emitting. The 国語大辞典 defines 星 as:
(1) 一般には太陽・月・地球を除く天体。広義には、すべての天体。狭義には恒星をいう。
So any astronomical objects excluding sun, moon and Earth – as Leebo said – but in a broader sense, any astronomical object. It is not uncommon for the Earth to informally be referred to as 星. One example is the title of this theme song of an animal documentary.
惑星 is by no means a science term or anything, but someone like Barret who uses crude and unrefined language, would probably rather use 星.
There’s another game I know of that uses 星 to refer to the literal planet Earth. (Full Japanese transcript.) For example, one of the first lines of the game:
「私のなは“ガイア”。この星の、全ての生物を見守り、共に生きて行き者…。」
(Converted to kanji for ease of reading, although the original game script uses mostly hiragana.)
I kind of suspect that writers are most likely to use 星 to refer to a planet, and in particular the one the speaker is walking around on (i.e., Earth), if they want to stress in the context of modern astronomy that the planet in question is just one among many in the universe. That’s true of the scientific/evolutionary plot in E.V.O., and of the environmental themes of FF7.
(Edit: I guess this more pertinent to why a writer would use 星 as opposed to a special term for Earth like 地球 than why they’d choose 星 over a more specific term like 惑星.)