noun
sidereal day
Astronomical term: the time it takes for the Earth to rotate once relative to the fixed stars, about 23 hours 56 minutes. Used in astronomy and related technical contexts.
恒星日は太陽日より約4分短い。
A sidereal day is about 4 minutes shorter than a solar day.
A solar day is based on the sun's position and is about 24 hours, while a sidereal day is based on the fixed stars and is about 23 hours 56 minutes.
Compound of 恒星 (fixed star) and 日 (day), a calque from Western astronomy.