Timeline of the Universe

Powerful telescopes such as ALMA probe to great distances, corresponding to ‘look-back times’ of billions of years in the past. However, by measuring the ages of stars in the earliest galaxies, it is possible to probe even further back in time. Such galaxies may have first ‘switched on’ when the Universe was only 250 to 350 million years old, and the birth of similar systems would be within reach of the James Webb Space Telescope when launched.