(a)[2]
State the equation used to define the average orbital speed $v$ of a planet. State the meaning of any symbols you use.
(b)[1]
Explain why countries that are a considerable distance from the Equator undergo marked temperature changes over the course of a year.
(c)[4]
Complete the paragraph about a star much more massive than the Sun by filling each gap with the correct stage. The stage that comes after the stable phase in the life cycle of the star is the [BLANK] stage. It then explodes as a supernova to form a [BLANK], which leaves behind a [BLANK] or a [BLANK].
(d)[2]
Calculate the distance between the galaxy and Earth. Give your answer in light-years.