Sidereal day

Definition

A sidereal day is the time it takes for Earth to rotate once relative to distant stars, approximately 23 hours, 56 minutes, and 4 seconds. It is different from a solar day, which is based on the position of the Sun in the sky.

5 Must Know Facts For Your Next Test

1. The sidereal day is about 4 minutes shorter than the solar day.
2. It is used by astronomers to track celestial objects because it aligns with Earth's rotation relative to stars.
3. A sidereal day represents one complete rotation of Earth on its axis.
4. Due to Earth's orbit around the Sun, each solar day is slightly longer than a sidereal day.
5. Sidereal time can be observed using a sidereal clock, which is synchronized with Earth's rotation relative to distant stars.

Review Questions

• What is the duration of a sidereal day in hours, minutes, and seconds?
• Why do astronomers prefer using sidereal days over solar days?
• How does Earth's orbit around the Sun affect the length of a solar day compared to a sidereal day?

Related terms

Solar Day: The time it takes for Earth to rotate once relative to the Sun, about 24 hours.

Sidereal Time: A time-keeping system that astronomers use based on Earth's rotation relative to distant stars.

Celestial Sphere: An imaginary sphere surrounding Earth where all celestial objects can be projected for observation.