AQA ยท A level Physics

Gravitational microlensing planet A-level challenge

Can you get 100%? Use the first TESS microlensing planet to test gravitational fields and how physicists judge a one-off brightness signal.

Read how TESS found a planet using microlensing

Want more practice after this? PhysicsUK membership unlocks the full pupil toolkit.

Question

8 marks

Answer all parts. Show your working and give units where appropriate.

1(a)

A foreground star passes close to the line of sight to a more distant star. Its gravitational field bends light from the distant star towards the telescope. Explain why the foreground star can change the apparent brightness even though it produces no glass-like material lens.

[2 marks]

1(b)

The foreground star has mass 1.6 x 10^30 kg. A light ray passes at a distance 2.0 x 10^11 m from the centre of the star. Calculate the gravitational field strength at the position of the ray. Use G = 6.67 x 10^-11 N m^2 kg^-2.

[3 marks]

1(c)

A planet orbiting the foreground star produces a short extra distortion in the otherwise smooth microlensing light curve. The same alignment is not expected to repeat. Explain how astronomers can test whether this short feature is evidence for a planet rather than measurement noise.

[3 marks]

Start the question to write your answer, receive marks and ask Sherlock Ohms for text help.