State what Hubble’s law says.
A star in a distant galaxy emits radiation whose maximum intensity of emission is at a wavelength of $4.62\times10^{-7}\,\text{m}$. Observations of the galaxy made on the Earth detect the star’s maximum emission intensity at a wavelength of $4.91\times10^{-7}\,\text{m}$.
Explain why the observed wavelength is different from the emitted wavelength.
Calculate the speed of the star relative to the Earth.
The wavelength of maximum intensity of emission is used to find a value for the star’s surface temperature. Explain how the temperature found from the observed wavelength compares with the true temperature value found from the emitted wavelength.
A value for the Hubble constant is $2.3\times10^{-18}\,\text{s}^{-1}$. Use your answer in (b)(ii) to find the distance of the star in (b) from the Earth.