siderial

Siderial refers to anything related to the stars or celestial bodies. In astronomy, a siderial day is the time it takes for the Earth to rotate once relative to the fixed stars. This is different from a solar day, which is the time it takes for the Earth to rotate once relative to the Sun. A siderial day is approximately 23 hours, 56 minutes, and 4 seconds long, while a solar day is 24 hours long. The difference is due to the Earth's revolution around the Sun.

The term siderial is also used in astrology. A siderial zodiac is based on the actual positions of the constellations in the sky, whereas a tropical zodiac is based on the seasons. The siderial zodiac is more accurate in reflecting the current positions of the stars, but the tropical zodiac is more commonly used.

In a broader sense, siderial can be used to describe anything that is vast, eternal, or cosmic in nature. It evokes a sense of timelessness and the immense scale of the universe.