Found the fuel of star formation?

A new study reports the observation of a river never seen before of cold hydrogen flowing into the space between the galaxies. This tenuous strand of gas detected in the vicinity of the nearby galaxy NGC 6946, may help to explain how some spiral galaxies are able to keep their constant rate of star formation.

NGC 6946

Composite image of the galaxy NGC 6946.


A placid river of tenuous gas, a filament spread of cold hydrogen has been found that could power the constant rate of star formation in many spiral galaxies. This is what was observed for the first time in the vicinity of the nearby galaxy NGC 6946 in a new research published in the Astronomical Journal.

The study was conducted by astronomer Daniel J. Pisano at West Virginia University using the powerful means of the gigantic Green Bank Telescope (GBT). The GBT, a symbol of American grandeur, is the most powerful radio telescope ever built. With its 100 meters in diameter, it provides a level of detail impossible to achieve with any other tool. Around the GBT extends the so-called National Radio Quiet Zone, an area of ​​about 34,000 square kilometers of land in West Virginia, where it is banned the use of any device to electromagnetic and radio waves in order to not disturb the giant in its work. For the complete package, the various funders and research institutions spend the modest sum of $ 10 million per year in operating costs.

Some previous studies had revealed an extended halo of hydrogen around NGC 6946; it was found in a cloud of hot gas, a consequence of the processes of star formation and supernova explosions, a common feature of spiral galaxies. A cold stream as the one found by Pisano, had never been observed before, and could be made up of hydrogen coming from a completely different process: the release of gas from the intergalactic space within the galaxies, which is supposed to be used to give life to the stars.

“We knew that the fuel for star formation had to come from somewhere. So far, however, we detected only 10 percent of what would be necessary to explain what we observe in many galaxies,” said Pisano. “The main theory is that these rivers may ferrying hydrogen gas in intergalactic space, fueling star formation. This tenuous strand of hydrogen was simply too widespread to be able to detect before now.”

According to theoretical models known for some time, the larger galaxies would receive a constant flow of cold hydrogen from the less massive companions. The one found by Pisano would seem to be the first experimental confirmation of the actual existence of neutral hydrogen bridges between galaxies. Then did we solve the mystery of star formation? Not really. The nature of the detected gas may in fact be just as likely to close the remainder of the encounter between NGC 6946 and some other galaxy, a “face to face” that may have left a trail of neutral hydrogen detected. In this case, however, the filaments should be populated at least from a handful of stars. New studies will be needed to solve this problem and shed light on the possible role that these filaments of cold hydrogen play in the evolution of galaxies.

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