Free Astronomy Magazine May-June 2018

52 MAY-JUNE 2018 SPACE CHRONICLES are built. It’s the glue that holds the visible matter in galaxies — stars and gas — together. “We thought that every galaxy had dark matter and that dark matter is how a galaxy begins,” said Pieter van Dokkum of Yale University in New Haven, Connecticut, lead re- searcher of the Hubble observa- tions. “This invisible, mysterious sub- stance is the most dominant aspect of any galaxy. So finding a galaxy without it is unexpected. It chal- lenges the standard ideas of how we think galaxies work, and it shows that dark matter is real: it has its own separate existence apart from other components of galaxies. This result also suggests that there may be more than one way to form First galaxy in the local Universe without dark matter by NASA/ESA G alaxies and dark matter go together like peanut butter and jelly. You typically don’t find one without the other. Therefore, researchers were sur- prised when they uncovered a gal- axy that is missing most, if not all, of its dark matter. An invisible sub- stance, dark matter is the underly- ing scaffolding upon which galaxies