NCERT Solutions Curiosity Chapter 12 .2 Revolution of the Earth — In-text Question
Book page 17512 Updated on2026-09-05
Q1.
But, why do different stars appear in the night sky over the course of a year?
Answer
Because the Earth is also revolving around the Sun. As it moves along its orbit, the night side of the Earth faces a different part of the sky in different months — so a different set of stars is on show after sunset.
At night we are always looking away from the Sun. In March that direction points at one region of the sky; three months later the Earth has travelled a quarter of the way round its orbit, so at night we look at a region roughly 90° away.
The night side always faces away from the Sun. As the Earth moves round its orbit, that direction sweeps through the whole sky in one year — so different stars are seen in different months.
Why it happens: the Earth takes about 365 days and 6 hours for one revolution. That is why the star patterns come back to the same place in the sky after one year, and why the book asked you in Grade 6 to look for particular constellations only in particular months.
Try this: look at the same part of the sky at the same clock time on the 1st of two months in a row. The stars will have shifted by about 30° — a quarter of a right angle more than a fist-width, and easy to notice.