Hertzsprung-Russell diagram and stellar life cyclesEdexcel A-Level Physics: Mind map

Exam questions on Hertzsprung-Russell diagram and stellar life cycles

1. A star, R, has a surface temperature of 3200 K and a luminosity 5.0 × 10² times that of the Sun. Astronomers plot its position on a Hertzsprung-Russell (HR) diagram, which shows luminosity against surface temperature.
   Explain why star R is much more luminous than the Sun even though its surface temperature is lower.2 marks
2. A cloud of cold gas and dust in space collapses and forms a star similar to the Sun, which then spends most of its life fusing hydrogen in its core.
   Explain why the star stays at a constant size and luminosity for most of its life.2 marks
3. A white dwarf has a surface temperature of 12 000 K and a luminosity 1.0 × 10⁻³ times that of the Sun. The luminosity of the Sun is 3.85 × 10²⁶ W.
   Calculate the radius of the white dwarf.3 marks