AQA GCSE Physics (8463), Higher tier · Space physics › Solar system, orbits and satellites
Practise Our solar system. 13 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Our solar system contains many different objects. How many planets orbit the Sun?
8
Name the process that releases energy in the core of the Sun.
Nuclear fusion
A star forms from a cloud of dust and gas. The statements A, B, C and D describe stages in the formation of a star. A Fusion reactions start in the core. B Dust and gas are pulled together by gravity. C The star becomes stable, with a constant size. D The collapsing cloud becomes denser and hotter, forming a protostar. Write the letters A, B, C and D in the correct order.
B, D, A, C
State what keeps the planets in orbit around the Sun.
The Sun's gravitational force.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Our solar system contains many different objects.
(a) How many stars are there in our solar system? Tick (✓) one box.[1]
1
8
9
Millions
(b) How many planets orbit the Sun?[1]
(c) What name is given to the natural satellites that orbit planets?[1]
(d) Our solar system is a small part of a galaxy. Name this galaxy.[1]
(e) Name one other type of object, apart from planets, that orbits the Sun.[1]
Show the answer and mark scheme
(a)Answer: 1
(b)Answer: 8
8 / eight
(c)Answer: Moons
moons
(d)Answer: The Milky Way
the Milky Way
(e)Answer: Dwarf planets (e.g. Pluto)
dwarf planet
Question 2Medium6 marks
The Sun formed about 4.6 billion years ago.
(a) Describe how the Sun was formed.[3]
(b) Name the process that releases energy in the core of the Sun.[1]
(c) The size of the Sun is stable because two effects are in equilibrium. Name these two effects.[2]
Show the answer and mark scheme
(a)Answer: A cloud of dust and gas was pulled together by gravity until it was hot and dense enough for fusion to start.
from a cloud of dust and gas (a nebula)
the dust and gas were pulled together by gravity / gravitational attraction
it became hot and dense enough for (nuclear) fusion to start
(b)Answer: Nuclear fusion
(nuclear) fusion
(c)Answer: Inward gravitational collapse and outward expansion due to fusion energy.
outward pressure / expansion caused by the energy released by fusion
Question 3Hard8 marks
At the start of a star's life cycle, dust and gas are drawn together by gravity.
(a) Explain how this leads to fusion reactions starting in the core of the star.[4]
(b) Explain why a main sequence star stays the same size for billions of years.[2]
(c) The planets formed from the same cloud of dust and gas as the Sun. Suggest why fusion did not start inside the planets.[2]
Show the answer and mark scheme
(a)Answer: Gravitational collapse transfers energy to the particles, heating the core until hydrogen nuclei move fast enough to overcome their repulsion and fuse.
as the cloud collapses, energy from the gravitational potential energy store is transferred to the kinetic energy store of the particles
so the temperature (and density) of the core increases
at very high temperatures, hydrogen nuclei move fast enough to overcome their (electrostatic) repulsion
so nuclei collide and fuse (forming helium and releasing energy)
(b)Answer: Fusion energy balances gravity for as long as hydrogen fusion continues in the core.
the outward pressure from fusion energy balances the inward gravitational force (equilibrium)
this continues for as long as there is hydrogen in the core to fuse
(c)Answer: They have far less mass, so their cores never became hot and dense enough for fusion.
the planets have much less mass than the Sun
so gravity did not compress / heat their cores enough; the temperature and pressure were too low for fusion