Cosmic gas flows act as "fuel superhighways" that allow massive stars to continue growing
How do the largest stars in the universe gain such mass, when their powerful radiation is supposed to eject incoming matter?
The giant stars
The universe is so vast that its size is beyond human comprehension. The size of our sun alone is staggering, with a mass that is more than 330,000 times that of Earth. But it is also dwarfed by other stars that are much more massive.
Stars that are more than eight times the mass of the Sun are classified as massive stars. These giants form rapidly, releasing powerful stellar winds and radiation. Under normal circumstances, such forces should eject matter, preventing the star from reaching such enormous sizes. Something is clearly fueling them, but scientists have wondered for years what the exact process is that causes the rapid growth.
The mystery of massive star formation
For years, astronomers have hypothesized that giant accretion disks (large, rotating structures of gas and dust around a star) provide the material that stars need to grow. But new research suggests a different answer.
"Our study shows that these structures are likely fed by flows of gas that bring material from distances exceeding a thousand astronomical units, essentially acting as massive gas highways," says corresponding author Fernando Olguin.
Gas highways feed stars
To test this idea, the researchers needed to see star-forming regions in much greater detail, because the places where massive stars form are farther away than those where small stars form. They turned to the powerful ALMA observatory in Chile, which consists of dozens of antennas that can detect faint emissions from dust and molecules at millimeter wavelengths.
Using ALMA's precision, the team observed a young star being fed by what appeared to be two separate flows. One of these flows connected directly to the central region of the star and showed a velocity pattern consistent with rotation and possibly inward collapse. This suggests that the flow is carrying enough material at a rapid rate to overcome the young star's emissions, building up the dense region found around its core.
Flows bring stellar fuel
The researchers expected to see a disk or ring of dust a few hundred astronomical units across, but they did not expect the spiral arms to come so close to the central source.
"We found flows feeding what at the time we thought was a disk, but to our surprise there is no disk or it is very small," says Olgin.
These results suggest that, regardless of the presence of a disk around the central star, flows can transport large amounts of gas to feed star-forming regions, even when there is emission from the central star.
Next, the team plans to expand the study to other regions and see if this is a common mode of adsorption that causes massive stars to form. They also plan to study the gas close to the star to determine whether they can confirm or rule out the presence of small disks.
More of the topic in Hayadan:
One response
There is always *more* to discover, we will never know *everything*.