I did a lot of googling last night. If you're familiar with Sailor Moon, you'll know that in the fifth season the Sailor Starlights
appear: Seiya Kou, Yaten Kou, and Taiki Kou. I've often wondered why they were given these names. I came across a website a long time ago which suggested that they were named after some sort of astronomical phenomena, but it didn't go into detail, and I was never able to find any further information.
However! Yesterday I found the Japanese Wikipedia page for yatenkou
. It turns out that yatenkou refers to the fact that the night sky is never completely dark, and there are three main factors contributing to this: taikikou, koudoukou, and seiyakou. Unfortunately, only one of these led to its own page, which in turn led to the English page: koudoukou (zodiacal light
, a kind of scattered sunlight). Which wasn't very helpful!
It took quite a bit of googling, but I finally decided that yatenkou referred to sky brightness
. Sky brightness is sometimes also called skyglow
, although that usually refers to a kind of light pollution that makes a dome of light over cities. On the 'sky brightness' page is a table listing the contributions to sky brightness: airglow
, zodiacal light, and scattered starlight. Airglow, according to Wikipedia, is 'the very weak emission of light by the Earth's atmosphere'. I think it's sometimes called the 'permanent aurora'.
So it seems to me that Seiya Kou = scattered starlight, Yaten Kou = sky brightness, and Taiki Kou = airglow. If I were to give them English names, I might go with something like Star Glow, Sky Glow and Air Glow. Or if the surnames should be different, maybe Star Shine, Sky Bright and Air Glow. I really do think about this too much...
I did wonder why the third factor, zodiacal light, wasn't a character. Maybe Koudou just isn't a good name. It occurred to me that Princess Kakyuu might represent that, but no, she's definitely a fireball meteoroid