Syllabus Points — Astronomy and Cosmology

25.1 Standard candles

1. understand the term luminosity as the total power of radiation emitted by a star
2. recall and use the inverse square law for radiant flux intensity $F$ in terms of the luminosity $L$ of the source $F = L / (4\pi d^2)$
3. understand that an object of known luminosity is called a standard candle
4. understand the use of standard candles to determine distances to galaxies

25.2 Stellar radii

1. recall and use Wien's displacement law $\lambda_{\max} \propto 1 / T$ to estimate the peak surface temperature of a star
2. use the Stefan-Boltzmann law $L = 4\pi\sigma r^2 T^4$
3. use Wien's displacement law and the Stefan-Boltzmann law to estimate the radius of a star

25.3 Hubble's law and the Big Bang theory

1. understand that the lines in the emission and absorption spectra from distant objects show an increase in wavelength from their known values
2. use $\Delta\lambda / \lambda \approx \Delta f / f \approx v / c$ for the redshift of electromagnetic radiation from a source moving relative to an observer
3. explain why redshift leads to the idea that the Universe is expanding
4. recall and use Hubble's law $v \approx H_0 d$ and explain how this leads to the Big Bang theory (candidates will only be required to use SI units)