Figure 26-18: A Timeline of Light in the Universe The oldest light that we can see today is the cosmic background radiation, which comes from a time 380,000 years after the Big Bang when the universe first became transparent. This light has a redshift of about z = 1100 and appears in the microwave spectrum. Some 400 million years later at a redshift of about z = 11 the first stars appeared; their light is now redshifted to infrared wavelengths. Galaxies formed more recently and can be seen at visible wavelengths.
(NASA; JPL-Caltech; and A. Kashlinsky, Goddard Space Flight Center)