Planetary configurations and periods
Answers are for parents and teachers.
1
If the greatest western (morning) elongation is 45°, by up to about how many hours does the planet rise before the Sun (15° per hour)?
3
2
Earth’s year is 360 days; an inner planet has T = 120 days. 1/S = 1/120 – 1/360 = 2/360. S = ?
180
3
An outer planet has T = 1080 days (simple year 360): 1/S = 1/360 – 1/1080 = 2/1080. S = ?
540
4
Why is an outer planet brightest at opposition?
It is closest to the Earth and shows its fully lit side.
5
Why does Venus stay close to the Sun and appear only in the morning or evening?
Because its orbit lies inside the Earth’s and its elongation never exceeds 47°.