Light Quiz – Stars can shift the light spectrum

Light Quiz – Stars can shift the light spectrum

Quiz

An interesting phenomenon becomes apparent when looking up at the stars in the night sky: The spectrum of light is shifted whenever a star or another radiation source moves towards us. This shift can serve as a basis to determine whether a star or radiation source is moving closer or further away from us.

When a star approaches the earth, the spectral lines are displaced towards

a) ... shorter wavelengths (blueshift)

b) ... longer wavelengths (redshift)

c) ... not at all

Answer a) is correct: The spectral lines are displaced towards shorter wavelengths (blueshift).

When a star or a radiation source moves closer to us, the light spectrum is shifted in such a way that the wavelengths of light are compressed. This physical phenomenon is referred to as blueshift. In the opposite case, i.e. when a star moves away, a redshift occurs because the wavelengths of light are stretched. This allows us to determine whether a particular star is approaching the earth or going away from it. Generally speaking, a cosmological redshift can be observed due to the expansion of the Universe. Blueshifts may nevertheless occur locally. A prime example: the Andromeda galaxy is headed towards the Milky Way.