Measuring astronomical distancesEdexcel A-Level Physics: Mind map

Exam questions on Measuring astronomical distances

1. An astronomer measures the position of a nearby star against the background of very distant stars. She repeats the measurement six months later and finds that the position of the nearby star appears to have shifted. The parallax angle of the star is 0.25 arcseconds.
   Explain why the astronomer repeats the measurement six months later.2 marks
2. A Type Ia supernova is observed in a distant galaxy. All Type Ia supernovae reach the same peak luminosity, 2.0 × 10³⁶ W. At its peak the intensity received at the Earth from this supernova is 1.0 × 10⁻¹⁴ W m⁻².
   Suggest why the distance to this supernova cannot be found using trigonometric parallax, and why a standard candle can be used instead.2 marks
3. A star, X, has a parallax angle of 0.050 arcseconds. The intensity of the light received from it at the Earth is 2.4 × 10⁻¹⁰ W m⁻². One parsec is 3.09 × 10¹⁶ m, and the luminosity of the Sun is 3.85 × 10²⁶ W.
   Calculate the distance to star X in parsecs and in metres.3 marks