How Giant Stars Are Born: Scientists Reveal Cosmic Gas Feeding Process
- Ritambhara K
- 3 days ago
- 3 min read
Hierarchical gas kinematic structures. Starting from the upper left and moving clockwise from large to small scales: upper left —"spiral-like" system; upper right — "bar-like" structure; lower right — rotating infalling envelope; lower left — accretion disk. (Image by SHAO)
For the first time, astronomers have captured a detailed picture of how vast streams of interstellar gas spiral inward to form the disks that give birth to massive stars — the cosmic giants that light up galaxies and reshape the universe.
In a breakthrough study, researchers from the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences have mapped, step by step, the journey of gas from thousands of astronomical units away down to the immediate surroundings of a forming star. Using the powerful Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, along with the Very Large Array (VLA) in the United States, the team has revealed for the first time how the universe’s biggest stars grow — not in chaos, but through an ordered, galaxy-like system of spiraling gas flows.
Unraveling the Growth of Stellar Giants
Massive stars — those exceeding eight times the Sun’s mass — are key drivers of cosmic evolution. Their intense radiation, stellar winds, and explosive deaths as supernovae reshape the surrounding interstellar medium, influencing how galaxies evolve.
Unlike smaller stars that emerge through relatively straightforward gravitational collapse, massive stars form within highly dynamic and turbulent gas environments. Until now, astronomers lacked a clear understanding of how gas travels step by step to create the accretion disks that feed these stellar giants.
Tracing Gas from Vast Distances to the Birth Disk
To solve this mystery, the SHAO team used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, paired with maser astrometry — a microwave-based technique for precisely measuring gas motion. They also incorporated data from the Very Large Array (VLA) in New Mexico, USA.
Together, these instruments allowed researchers to trace gas inflow from about 2,500 astronomical units (AU) down to 40 AU — a span covering from the outer regions of a stellar nursery to near the forming star itself. (One AU equals the distance between Earth and the Sun.)
A Miniature Galaxy Inside a Stellar Nursery
The team focused on the massive star-forming region IRAS 18134-1942, located roughly 1.25 kiloparsecs from the Sun. Their observations unveiled a layered, hierarchical system of gas flows that mirrors the structure of a spiral galaxy on a smaller scale.
At large distances, spiral-like streams of gas channel material inward, shaped by the rotation and collapse of the parent cloud. These merge into an elongated, bar-like structure that funnels gas toward the center. Closer in, gas forms a rotating envelope that eventually transitions into a Keplerian accretion disk within a few hundred AU.
This entire sequence, the researchers noted, resembles a barred spiral galaxy embedded within a molecular cloud — a miniature cosmic system building a stellar giant.
How Efficiently Do Massive Stars Grow?
The study also found that the rate of gas transport remained around one ten-thousandth of a solar mass per year in the outer spiral and bar regions but dropped to roughly one millionth of a solar mass per year at the disk scale. This suggests that the envelope and disk act as regulators, controlling how efficiently the protostar accumulates mass.
Interestingly, the rotation axis of the surrounding envelope was tilted relative to the disk, indicating a misalignment likely caused by turbulent inflows bringing uneven angular momentum — not a reversal, but a subtle twist in the gas dynamics.
A Galactic Pattern in Stellar Birth
“Our results show that the internal structures of massive molecular cloud clumps are not random or chaotic, but can form highly ordered, galaxy-like patterns,” said Dr. Mai Xiaofeng, first and corresponding author of the study. “This provides crucial observational evidence for how massive stars gather mass and build accretion disks in complex environments.”
Part of a Global Effort
The research is part of the ALMA-ATOMS/QUARKS survey, an international collaboration that has collected multiscale data from over 140 massive star-forming regions in the past five years.
“We are now analyzing more systems with ALMA and conducting follow-up studies alongside advanced simulations,” said Dr. Liu Tie, project leader and co-corresponding author. “Together, these efforts will help us piece together the complete picture of how the universe’s biggest stars are born.”
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