Complete the following sentences about our Solar System and the wider Universe:

1. The attractive force that provides the centripetal force keeping moons in orbit around their parent planets is the \text{________________} force.

2. Two types of astronomical bodies, other than planets or dwarf planets, that orbit our Sun are \text{________________} and \text{________________}.

3. The Milky Way, which contains our Solar System, is a large collection of stars, dust, and gas held together by gravity, known as a \text{________________}.

The diagram shows the highly eccentric elliptical orbit of a comet as it travels around a central star, Star $S$. Points $A$, $B$, $C$, and $D$ are positions along its orbital path.

Draw on this

(i) At which of the points shown is the magnitude of the gravitational force exerted on the comet by Star $S$ the greatest?

(ii) At which of the points shown does the comet have the greatest kinetic energy?

(iii) At which of the points shown does the comet have the greatest gravitational potential energy?

(iv) State the direction of the gravitational force acting on the comet when it is at point $D$.