Using Wien's Law we can determine the lambda max for blackbodies with different temperatures. The Doppler effect occurs when objects, which are emitting any kind of waves, are in motion. Motion towards you will shorten the wavelength of the waves. Motion away from you with increase the length of the waves. Redshift and blueshift in the spectral lines of celestial objects are due to the Doppler effect, that is, they are caused by the motion of these objects away from and towards us.
Redshift is the shift of spectral lines toward longer wavelength.
Blueshift is the shift of spectral lines toward shorter wavelength. We can learn whether a celestial body is moving radially toward or away from us and its radial speed, by knowing whether its spectral lines show a blueshift or a redshift, respectively. According to the Doppler effect, a redshift implies that the object is moving away from us, and a blueshift implies that the object is moving toward us. Spectral lines tell astronomers what atoms and molecules are present and how much of each there is. Astronomers can determine the lambda max of the spectra.