The correct answer is D. All of the above.
A sidereal day is the time it takes for the Earth to rotate once on its axis relative to a distant star. It is slightly shorter than an ordinary solar day, which is the time it takes for the Earth to rotate once on its axis relative to the Sun. This is because the Earth is also orbiting the Sun, so it has to travel a little further in its orbit during a solar day than it does during a sidereal day.
A sidereal day is divided into the conventional hours, minutes and seconds, just like a solar day. However, the length of a sidereal hour is slightly shorter than a solar hour, because there are 24 sidereal hours in a sidereal day, but only 23.93 solar hours in a solar day.
Here is a more detailed explanation of each option:
- Option A: A sidereal day is the period of time taken by the earth in making a complete rotation with reference to stars. This means that if you were to stand on a point on the Earth’s surface and look at a star, the star would appear to move across the sky in a circle. It would take one sidereal day for the star to return to its original position in the sky.
- Option B: A sidereal day is slightly shorter than an ordinary solar day. This is because the Earth is also orbiting the Sun. As the Earth orbits the Sun, it also rotates on its axis. This means that the Earth is moving in two directions at once: it is moving around the Sun, and it is also rotating on its axis. The combination of these two motions causes the Earth’s day to be slightly longer than a sidereal day.
- Option C: A sidereal day is divided into the conventional hours, minutes and seconds. This means that a sidereal day is 24 hours long, each hour is 60 minutes long, and each minute is 60 seconds long. However, the length of a sidereal hour is slightly shorter than a solar hour, because there are 24 sidereal hours in a sidereal day, but only 23.93 solar hours in a solar day.