Final answer:
The student's question pertains to which star lies closest to the south celestial pole. While specifics of question 4 are not provided, a general explanation involves using the constellations to approximate the location since there is no bright star like Polaris marking the south celestial pole.
Step-by-step explanation:
The question from the student asks which star lies closest to the south celestial pole on the celestial sphere. While the specific answer to question 4 is not provided in the information given, we can offer a general explanation of how to determine the position of stars relative to the south celestial pole.
The celestial sphere is an imaginary sphere where the Earth is at its center and all the celestial bodies (like stars, planets, and the Moon) are considered to be placed upon it. The south celestial pole is the point in the sky directly above the Earth's South Pole.
Stars near the south celestial pole will appear to circle around the pole due to the Earth's rotation. However, unlike Polaris in the northern sky, there is no particularly bright star marking the south celestial pole. Due to the absence of a 'southern Polaris', identifying the south celestial pole's location involves locating the southern cross constellation (Crux) and then using it to approximate where the pole would be.
As shown in Figure 2.4, stars appear to move in circular paths around the south celestial pole, and a long-exposure photo can capture these trails, indicating their movement around the pole.