Dawn after the dark age

摘要

The latest surveys provide evidence for one, maybe two, galaxies farther back in cosmic time than ever detected before. But does the fact that we don't see more mean these are the very first galaxies to be formed? Determining when the first stars andgalaxies formed is a matter of profound importance: fuelled by primordial hydrogen, these bodies triggered the nucleosynthesis of the heavier elements, such as carbon, nitrogen and oxygen, that are the basis of life. By studying the first galaxies, we can also hope to understand how the Universe formed and evolved, and detect the younger progenitors of galaxies like our own Milky Way, In this issue, lye et al. (page 186) report the discovery of the most distant galaxy yet, one whose photons must have left it 12.7 billion years ago, when the Universe was just 750 million years old, and some 8 billion years before the Sun and Earth were formed. And Bouwens and Illingworth (page 189) report on their search for galaxies even farther away, more than 13 billion light years from Earth.