Question

During the night, as viewed from a point 20° south of the equator, most stars

a.	rise in the east and set in the west.

b.	move in retrograde motion across the sky.

c.	rise in the south and set in the north.

d.	no general statement can be made.

e.	rise in the west and set in the east.

Answer 1

The Earth takes 24 hours to spin about its axis. As viewed from north pole, the earth rotates counter clockwise or eastward. Therefore, if we observe the sky during the night, we can notice that stars are rising in the east and setting in the west. There are also exceptions because some stars are near the north and the south poles. If the pole’s position is far above the horizon, some stars may not set. Note that if viewed from 20 degree south of equator the stars will rise in the east along a slanted line making an angle of 20 degree with the equator and will set in the west along a line making an angle of 20 or 160 degree (depending on the convention) with the equator. Here we have neglected the motion of stars and talked about something which results from the earths spinning about it's axis. Therefore, correct option is (a).