noun
Chinese "Room" constellation (28 mansions)
Archaic astronomical term for the 房宿, the 4th of the 28 Chinese lunar mansions. Used in classical Japanese astronomy and astrology.
添い星は二十八宿の一つで、房宿にあたる。
Soiboshi is one of the 28 mansions, corresponding to the Room mansion.
noun
natural satellite; moon
Only when written 添い星 / 添星
Archaic term for a natural satellite or moon, restricted to the kanji forms 添い星 and 添星. Replaced by 衛星 in modern Japanese.
See also: 衛星
昔は月のことを添い星と呼ぶことがあった。
In the past, the moon was sometimes called soiboshi.
The reading そいぼし likely derives from 添い (accompanying) + 星 (star), possibly referring to a star that accompanies another celestial body. The exact historical derivation is uncertain.