Credit: Pieter van Dokkum, Roberto Abraham, Gemini, Sloan Digital Sky SurveyBy Shannon HallThe Milky Way has a dark twin. A dimly lit massive galaxy, called Dragonfly 44, consists of a record 99.99 per cent dark matter, and could help rewrite our theories of galaxy formation. Dragonfly 44 is the Milky Way’s doppelgänger in mass, but its opposite in...