Giant structures stretching more than a billion light years across have been revealed by two new maps of the distribution of galaxies in the universe. The updated atlases lend more support to the idea that the universe is dominated by dark matter and dark energy. Both studies used data from the Sloan Digital Sky Survey to gather the colour and position in the sky of more than a million galaxies. But in order to understand galaxy distribution in three dimensions, researchers must also know the distance between each galaxy and the Earth. That can be done by collecting a spectrum for each and every galaxy to see how the expansion of the universe stretches its light waves on the way to Earth, but is very time consuming and expensive. So the teams that produced the new maps sidestepped that process by finding automatic ways to assign distances to hundreds of thousands of galaxies without having to collect all those spectra. They looked at a class of bright, very old galaxies – called luminous red galaxies – which have well known true colours. Distortions in their colour are therefore easily measured, meaning their distances from Earth can be […]