There's a Massive River of Hydrogen Running Through Space

By Jamie Condliffe on at

An astronomer from West Virginia University has discovered a never-before-seen river of hydrogen flowing through space—and it could explain why spiral galaxies keep up their pace of star formation.

Working at the National Science Foundation's Robert C. Byrd Green Bank Telescope, astronomer D.J. Pisano has spotted a tenuous filament of hydrogen steaming through space and into galaxy NGC 6946. Previous studies have located extended halos of hydrogen around the galaxy, but this is the first time a river of the stuff has been spotted. Pisano explains:

"We knew that the fuel for star formation had to come from somewhere. So far, however, we've detected only about 10 per cent of what would be necessary to explain what we observe in many galaxies. A leading theory is that rivers of hydrogen — known as cold flows — may be ferrying hydrogen through intergalactic space, clandestinely fueling star formation. But this tenuous hydrogen has been simply too diffuse to detect, until now."

The Green Bank Telescope allowed Pisano to detect the faint glow emitted by neutral hydrogen streaming into NGC 6946, which just happened to be below the detection threshold of other telescopes. The finding may confirm the theories of astronomers past, which suggested that larger galaxies could receive an influx of cold hydrogen from other, nearby celestial bodies via cold flows as a means of fuelling their growth.

Quite how the flow came to be set up—and therefore, how common an occurrence it might be—remains unknown, though. Further research should help reveals its secrets, and potentially explain exactly how some spiral galaxies do keep up their incredible pace of star formation. [The Astronomical Journal via Science Daily]

Image by D.J. Pisano (WVU); B. Saxton (NRAO/AUI/NSF); Palomar Observatory – Space Telescope Science Institute 2nd Digital Sky Survey (Caltech); Westerbork Synthesis Radio Telescope