Question

You note that a particular star is directly overhead. It will be directly overhead again in

a. 1 hour
b. 12 hours
c. 23 hours 56 minutes
d. 24 hours
e. 24 hours 4 minutes

Answer 1

A star that rises at 8:30 p.m. tonight would rise approximately 4 hours earlier, around 4:30 p.m., two months from now due to the concept of sidereal time which is 4 minutes less than a solar day.

Step-by-step explanation:

When considering how the sky appears to turn due to the Earth's rotation, the concept of sidereal time and solar time is crucial. Stars like Sirius make a complete circuit in the sky every 23 hours and 56 minutes, which is slightly less than the solar day of 24 hours. Since stars rise and set 4 minutes earlier each day, we can calculate the change in rising time over a period of two or three months.

If a star rises at 8:30 p.m. today, it will rise approximately 4 minutes earlier each subsequent night. Over the course of two months (about 60 days), this would add up to 240 minutes, or 4 hours. Thus, two months from now, the star would rise at around 4:30 p.m. instead of 8:30 p.m.

Keeping track of when stars rise and set is a key part of astronomical observation and understanding the motion of the celestial sphere.