State Wien’s displacement law. Identify any symbols that you use.
A cosmology student observes the electromagnetic radiation received from a star in a galaxy. The student uses Wien’s law to estimate the surface temperature of the star, a standard candle to estimate the distance to the galaxy, and the Stefan–Boltzmann law to estimate the radius of the star. The student observes that the radiation from the star is redshifted.
State what is meant by a standard candle.
State the reason why the radiation from the star is redshifted.
is the peak wavelength, 
is the thermodynamic temperature of the body and 
is Wien's constant.
