Dark galaxies observed for the first time

Talking Points Memo : Composed mainly of hydrogen and dust, dark galaxies have until now been impossible to detect because they lack any detectable stars. Using the Very Large Telescope, an international team of astronomers has captured a series of long exposures of a region of the sky illuminated by a quasar, one of the most luminous objects in the universe. They were able to identify some 12 distinct galaxies by the glow emitted by their hydrogen gas when bombarded by the quasar’s UV light. Because dark galaxies are thought to be in an early stage of evolution, their study could shed light on how universes form. The team’s results appear in the Monthly Notices of the Royal Astronomical Society.