Space Physics (AQA GCSE Physics Triple Paper 2)

What is the Sun?

A star at the centre of our solar system, a massive ball of hydrogen undergoing nuclear fusion.

What are the planets in our solar system in order from the Sun?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

What is a moon?

A natural satellite that orbits a planet.

What is a satellite?

Any object that orbits another in space; can be natural (like moons) or artificial.

What is a dwarf planet?

A body that orbits the Sun but is not large enough to clear its orbit of other objects (e.g., Pluto).

What force keeps planets and satellites in orbit?

Gravitational force from the body they orbit.

What causes gravity between two objects?

Their masses; more massive objects exert stronger gravitational forces.

Why do objects in orbit travel at a constant speed but constantly change direction?

Because gravity causes a constant centripetal force, pulling them toward the centre, changing their direction.

How does the speed of a satellite change with its orbital radius?

Lower orbit = faster speed; higher orbit = slower speed (to balance gravitational pull).

What is a stable orbit?

An orbit where the gravitational force provides the exact centripetal force needed to stay in a curved path.

Why do artificial satellites in low orbit travel faster than those in high orbit?

Because the gravitational force is stronger closer to Earth, so they must move faster to stay in orbit.

What are the two types of artificial satellite orbits?

Geostationary (high, fixed above equator) and low polar (close to Earth, passes over poles).

What is a geostationary satellite used for?

Communication – it remains above the same point on Earth.

What are low orbit satellites used for?

Earth observation, weather monitoring, spying, environmental tracking.

What is the life cycle of a star like the Sun?

Nebula → protostar → main sequence → red giant → white dwarf → black dwarf.

What is a nebula?

A large cloud of gas and dust in space, where stars are born.

How is a protostar formed?

Gravity pulls gas and dust together, increasing temperature and pressure until nuclear fusion starts.

What happens in the main sequence stage?

Outward pressure from fusion balances the inward pull of gravity; the star is stable.

What happens when a main sequence star runs out of hydrogen?

It expands into a red giant and fuses heavier elements.

What happens to a star like the Sun after the red giant phase?

It sheds its outer layers and becomes a white dwarf, which eventually cools to a black dwarf.

How is a massive star's life cycle different?

Nebula → protostar → main sequence → red supergiant → supernova → neutron star or black hole.

What causes a supernova?

A massive star collapses when it runs out of fuel, triggering an enormous explosion.

What is left behind after a supernova?

Either a neutron star or, if massive enough, a black hole.

What is a neutron star?

A very dense core of neutrons left after a supernova.

What is a black hole?

A region of space with gravity so strong not even light can escape; formed from the collapse of a very massive star.

What elements are formed during a star’s lifetime?

Light elements (like helium) are formed during fusion; heavier elements (up to iron) are made in red giants; elements heavier than iron form in supernovae.

How are elements distributed throughout the universe?

By supernova explosions, which scatter them into space.

Why is gravity essential in star formation?

It pulls gas and dust together to form protostars and maintains the structure of stars and planetary orbits.

What provides the energy in stars?

Nuclear fusion of hydrogen into helium in the core.

What is red-shift?

The stretching of light waves from galaxies moving away, causing them to appear redder.

What does red-shift tell us about the universe?

Distant galaxies are moving away from us; the universe is expanding.

What is the Big Bang theory?

The theory that the universe began from a very small, hot, dense point and has been expanding ever since.

What evidence supports the Big Bang theory?

Red-shift of galaxies and cosmic microwave background radiation (CMB).

What is cosmic microwave background radiation (CMB)?

Radiation left over from the early stages of the universe, a key piece of evidence for the Big Bang.

What does the Big Bang theory suggest about the future of the universe?

It will continue to expand, but how fast depends on factors like dark matter and dark energy.

What is dark matter?

Matter that doesn’t emit light or energy but has mass and affects gravity in galaxies.

What is dark energy?

A mysterious force thought to be causing the accelerated expansion of the universe.

How do astronomers measure the distance to far-off galaxies?

Using red-shift and Hubble’s Law (speed of recession is proportional to distance).

How do we know the universe is still expanding?

Galaxies are still red-shifted, and the further away they are, the faster they are receding.

What is meant by the observable universe?

The part of the universe we can see, limited by the speed of light and age of the universe.