The Milky Way galaxy is a staggering 1.9 million light years across, according to a new study, but most of it is made up of dark matter. The rest of the Milky Way is made up of the invisible 'dark matter halo' - that is a vast sphere of dark matter enveloping the galactic disc than can't be directly observed. 'In many analyses of the Milky Way halo its outer boundary is a fundamental constraint,' Deason wrote in the paper. The simulations allowed them to model the way the Milky Way's dark matter halo would look and interact with other objects. They doubled that figure to get the diameter of the dark matter halo surrounding hte Milky Way - and the actual full diameter of the Milky Way - 1.9 million light-years.

Source: Daily Mail March 24, 2020 13:26 UTC