Researchers from the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences have revealed for the first time how gas flows from vast distances toward the disk surrounding a nascent massive star in the process of star formation.

Massive stars—with more than eight times the mass of the Sun—play a decisive role in cosmic evolution. Their strong radiation, stellar winds, and eventual supernova explosions profoundly reshape the interstellar medium, driving galaxy structure and evolution. Unlike low-mass stars that typically form through relatively simple gravitational collapse, however, massive stars arise within highly dynamic, large-scale gas environments. The step-by-step process of gas transport to form accretion disks had not previously been understood.

The researchers used the Atacama Large Millimeter/submillimeter Array (ALMA), combined with maser astrometry—a way to measure the positions of gas using microwaves—to trace the complete process of gas accretion in a massive star-forming region. The microwave data came from the Very Large Array (VLA)—a world-class radio telescope in New Mexico, USA.

The researchers traced gas inflow from ~2,500 astronomical units (AU) to ~40 AU from the protostar. (One AU is the average distance between the Earth and the Sun.) Their findings, published on September 17 in Science Advances, were hailed by reviewers as a “textbook case” for understanding the hierarchical structure and gas accretion processes in massive star formation.

The researchers made their multiscale, high-resolution observations in the massive star-forming region IRAS 18134-1942, located about 1.25 kiloparsecs from the Sun. Their results reveal a striking layered system of gas flows: At the largest scales, multiple spiral-like streams channel material inward, shaped by the rotation and collapse of the parent cloud. These streams converge into an elongated, bar-like structure that funnels gas further toward the center. Closer in, the gas forms a rotating, collapsing envelope, and finally, within a few hundred AU, settles into an accretion disk exhibiting Keplerian rotation. This entire progression resembles a miniature barred spiral galaxy embedded within a molecular cloud.

The researchers also showed that the rate of gas transport stayed around one ten-thousandth of a solar mass per year in the “spiral” and “bar” structures but decreased to about one millionth of a solar mass per year at the disk scale. This suggests that the envelope and disk together regulate the efficiency of protostellar growth. Moreover, the rotation axis of the envelope is tilted in the opposite sense from the protostellar disk—not a true reversal of direction, but a misalignment likely caused by turbulent inflows delivering uneven angular momentum.

“Our results show that the internal structures of massive molecular cloud clumps are not random or chaotic, but can exhibit highly ordered, galaxy-like hierarchical patterns,” said Dr. MAI Xiaofeng of SHAO, first and corresponding author of the study. “This provides crucial observational evidence for how massive stars gather mass and form accretion disks in complex environments.”

The study is part of the international ALMA-ATOMS/QUARKS survey, which has collected multiscale data from over 140 massive star-forming regions over the past five years.

“We are now analyzing more systems with ALMA and follow-up observations, together with advanced numerical simulations, to further uncover the complete picture of massive star formation,” said Dr. LIU Tie, project leader and co-corresponding author of the study.

DOI：https://www.science.org/doi/10.1126/sciadv.ady6953

Contact：

MAI Xiaofeng： maixf@shao.ac.cn  

LIU Tie： liutie@shao.ac.cn