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Astronomers estimate that there are between 100 billion and 200 billion galaxies in the known universe. A single galaxy such as the Milky Way contain upwards of 200 billion normal stars. About 75 percent of of all stars in the Milky Way are less than half as massive as our Sun. In the universe at large, the majority of galaxies are classified as dwarfs, each with less than a few hundred million stars. The image above is a computer simulation of a colliding dwarf galaxy triggering the formation of the Milky Ways spiral arms. The largest project ever undertaken to map out the Universe in three dimensions using ESO telescopes has reached the halfway stage. An international team of astronomers has used the VIMOS instrument on the ESO Very Large Telescope to measure the distances to 55 000 galaxies as part of the VIPERS survey (VIMOS Public Extragalactic Redshift Survey). This has already allowed them to create a remarkable three-dimensional view of how galaxies were distributed in space in the younger Universe. This reveals the complex web of the large-scale structure of the Universe in great detail. The light of each galaxy is spread out into its component colours within VIMOS. Follow up analysis then allows astronomers to work out how fast the galaxy appears to move away from us — its redshift. This in turn reveals its distance and, when combined with its position on the sky, its location in the Universe.