Question

The interval of time that elapses between two consecutive passages of a fixed star (other than the sun) across the meridian is called

• A. mean solar day
• B. mean sidereal day
• C. mean solar year
• D. mean sidereal year

Answer 1

Answer: (B)

mean sidereal day

The time that the Earth takes to rotate about its axis so that the distant stars appear in the same position is called a sidereal day. Note that we treat the stars to be attached to the imaginary celestial sphere at a very large distance from the Earth.
An Earth day is 24 hours and hence a sidereal day will be 4 minutes faster.
The interval of time that elapses between two consecutive passages of a fixed star (other than the sun) across the meridian is called mean sidereal day.