(a) Describe the life cycle of a star with a similar mass to the Sun, from its formation to the end of its life. [4]
(b) Describe how the end of the life cycle of a star much more massive than the Sun is different. [2]
- (a) forms from a cloud of dust and gas / nebula (pulled together by gravity) ignore protostar(1)
- (a) (becomes a) main sequence star (hydrogen fusion; stable for a long time) allow 'stable star'(1)
- (a) (when hydrogen runs out it expands to become a) red giant(1)
- (a) (outer layers are lost and the core becomes a) white dwarf ignore 'cools to a black dwarf'; stages must be in the correct order: max 3 for (a) if the sequence is wrong(1)
- (b) any two from: becomes a red supergiant (instead of a red giant); explodes as a supernova; leaves a neutron star or a black hole (instead of a white dwarf) do not credit 'red giant' (this is not a difference); allow 'explodes' for supernova — first point(1)
- (b) second, different, point from the list above(1)
- Answer: (a) nebula → main sequence star → red giant → white dwarf (b) red supergiant → supernova → neutron star or black hole
- Examiner tip: Stages must be in the right order; the Sun will not become a supernova or a black hole.