The discovery of a faint filament of hydrogen gas streaming across space could help to explain how some galaxies maintain their pace of star formation.
D. J. Pisano from West Virginia University in Morgantown used the Robert C. Byrd Green Bank Telescope to identify a river of hydrogen connecting the galaxy NGC 6946 (pictured) with its neighbours. Pisano suggests that the filament could be the first observation of a 'cold flow', a stream of diffuse gas from intergalactic space that has long been theorized to be a source of fuel for star formation, and that is invisible to most telescopes.
Alternatively, the hydrogen could have been drawn out during a close encounter between NGC 6946 and its neighbours. Future galaxy surveys should confirm the source of this hydrogen stream.