A never-seen-before river of hydrogen flowing through space was discovered by West Virginia University researchers.
The discovery was made by the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT). Researchers describe the river as a faint tenuous filament of gas streaming into the nearby galaxy NGC 6946 and are hopeful that this discovery will help them better understand how certain spiral galaxies keep up their steady pace of star formation.
"We knew that the fuel for star formation had to come from somewhere. So far, however, we've detected only about 10 percent of what would be necessary to explain what we observe in many galaxies," astronomer D.J. Pisano said in a press statement. "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."
Unlike the Milky Way, which maintains a steady pace of star formation, galaxies like NGC 6946 (located 22 million light years from Earth) are more active when it comes to star formation. However, both these galaxies are categorized as spiral galaxies, which lead researchers to question what is fueling the star formation in all similar spiral galaxies.
Using the GBT, Pisano was able to detect the glow emitted by neutral hydrogen gas connecting NGC 6946 with its cosmic neighbors. This signal was simply below the detection threshold of other telescopes. The GBT's unique capabilities, including its immense single dish, unblocked aperture, and location in the National Radio Quiet Zone, enabled it to detect this tenuous radio light.
Earlier studies that looked into the galactic neighborhood around NGC 6946 found an extended halo of hydrogen nearby. However, this cold flow of the gas could mean that the hydrogen came from a completely different source rather than being hydrogen ejected from the disk of the galaxy by intense star formation and supernova explosions.
"In looking at NGC 6946, the GBT detected just the sort of filamentary structure that would be present in a cold flow, though there is another probable explanation for what has been observed. It's also possible that sometime in the past this galaxy had a close encounter and passed by its neighbors, leaving a ribbon of neutral atomic hydrogen in its wake," the press release stated.
The recent discovery is quite puzzling for scientists, giving rise to many new questions and leaving previous ones unanswered. Researchers hope that further studies could help confirm the nature of this observation and shed light on the possible role that cold flows play in the evolution of galaxies.
