AQA GCSE Physics: Space Physics

A star with a mass much greater than the Sun (more than about 8 times the Sun's mass) reaches the end of its life very differently from a star like the Sun.

Describe the life cycle of such a high-mass star, from its formation in a nebula to its final state. In your answer you should refer to nuclear fusion, the role of gravity, the supernova, and the possible final states of the star. (6 marks)

Light from distant galaxies shows red-shift. Astronomers measure the observed wavelength of a particular absorption line in the light from four galaxies and compare it with the wavelength of the same line measured in a laboratory on Earth (486 nm).

Galaxy	Observed wavelength of line / nm
A	489
B	495
C	506
D	521

(a) State what is meant by red-shift, and explain what these observations show about the motion of the galaxies. (2 marks)

(b) Using the data, state which galaxy is moving away from us fastest, and give a reason. (1 mark)

(c) State what the red-shift of nearly all galaxies tells us about the universe as a whole. (1 mark)

A planet orbits the Sun in a roughly circular orbit at a constant speed.

(a) Name the force that keeps the planet in orbit around the Sun. (1 mark)

(b) The planet moves at a constant speed, yet it is constantly accelerating. Explain how this is possible. (2 marks)

The Big Bang theory is the currently accepted scientific explanation for the origin of the universe.

(a) State one observation, other than red-shift, that provides evidence for the Big Bang theory. (1 mark)

(b) Briefly describe what the Big Bang theory says about how the universe began. (2 marks)

For an object in a stable circular orbit around a planet, the closer the orbit is to the planet, the faster the object must travel.

Explain why an object in a lower (smaller-radius) orbit must move faster than one in a higher orbit to stay in a stable orbit. (2 marks)

A star like the Sun is currently in the longest and most stable stage of its life cycle.

Name this stage. (1 mark)