Red-shift
Emission spectra
Light from a star does not contain all the wavelengths of the The different types of electromagnetic radiation, arranged in order of frequency or wavelength.. Elements in the star absorb some of the emitted wavelengths, so dark lines are present when the spectrum is analysed. Different elements produce different patterns of dark lines. The diagram shows part of the emission spectrum of light from the Sun.
Spectra from distant galaxies
Astronomers can observe light from distant A cluster of billions of stars, held together by gravity.. When they do this, they see it is different to the light from the Sun. The dark lines in the spectra from distant galaxies show an increase in wavelength. The lines are moved or shifted towards the red end of the spectrum. This effect is called The change in wavelength of light from a distant star moving away from Earth.. The diagram shows part of the emission spectrum of light from a distant galaxy.
Red-shift and speed
Astronomers see red-shift in virtually all galaxies. It is a result of the space between the Earth and the galaxies expanding. This expansion has the effect of increasing the wavelength of the light from these galaxies, shifting them towards the red end of the spectrum. The more red-shifted the light from a galaxy is, the faster the galaxy is moving away from Earth.