'Sky Eye' helps unlock mysteries of the universe

Using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), or the "China Sky Eye", Chinese and international astronomers observed a complex filamentary structure network dominated by supersonic turbulence within an interstellar gas cloud moving at ultrahigh speed in the Milky Way.

Such results have provided new insights into revealing the material sources and evolutionary pathways of the interstellar clouds, where new stars and planets form and secrets related to the birth of the solar system may hide, said the Shanghai Astronomical Observatory of the Chinese Academy of Sciences.

A paper about the research was published on the website of the journal Nature Astronomy on Wednesday.

FAST was independently designed and constructed by China and is the world's largest single-dish radio telescope. The target of this observation was a very-high-velocity cloud, G165, composed of hydrogen atoms, and hurtling through the outer regions of the Milky Way at a speed of approximately 300 kilometers per second.

Experts explained that positioned in a remote and isolated environment, G165 experiences minimal disruption from common factors, such as stellar radiation and gravitational disturbances, making it an ideal natural laboratory for studying the formation and evolution of interstellar clouds in their early stages.

The exceptional sensitivity and spatial resolution of FAST enabled scientists to unveil structural details within the very-high-velocity cloud to an unprecedented extent. Unlike typical clouds of this kind, characterized by a significant mix of cold and warm gases, G165 is predominantly composed of warm neutral gas with minimal to negligible cold neutral gas components. The difference suggests that very-high-velocity clouds with G165 as a representative were in an earlier stage of interstellar cloud evolution, said the researchers.

Surprisingly, although previous studies indicated that the interior of the warm neutral medium should be calm and uniform, researchers identified highly structured features within G165, including intricate interwoven filamentary structures. Distributed in a mesh-like pattern across multiple velocity layers, such structures suggest the presence of shock compression processes within G165, exhibiting strong turbulent characteristics throughout the system.

Further studies led by Li Beicheng, a researcher with the Shanghai Astronomical Observatory, showed that with the interaction of magnetic fields, supersonic turbulence can naturally generate filamentary structures and dynamic gas behavior consistent with the observed results.

"This process doesn't require the involvement of gravity, indicating that turbulence and magnetic fields may play a dominant role in shaping the structure of interstellar clouds during their early stages, providing crucial clues to understanding the physical mechanisms behind the early formation of interstellar clouds," Li said.

Scientists said this research breakthrough offers vital observational evidence for understanding the organizational mechanism of atomic gas in the outer regions of the Milky Way and material cycling on galactic scales.