China’s Five-hundred-meter Aperture Spherical radio Telescope (FAST) has achieved a significant breakthrough in astronomy. FAST has produced the largest-ever atlas of neutral hydrogen sources across the universe, according to a report.

The milestone marks a significant step in humanity’s effort to understand how galaxies form, evolve and interact on the largest scales.

Reports revealed that the FAST detected 156,411 neutral hydrogen sources during two years of observations. The observations cover approximately 19,500 square degrees of the sky—nearly half of the entire celestial sphere.

Neutral hydrogen is one of the most fundamental forms of matter in the universe. Often described as the raw material from which stars and galaxies develop, it also preserves information about the evolution of the cosmos.

Astronomers can detect neutral hydrogen through the characteristic 21-centimeter radio emission it produces. Unlike visible light, radio waves at this wavelength can pass through significant amounts of cosmic dust, allowing scientists to observe gas that may otherwise remain hidden.

FAST is particularly well suited to this task because of its enormous collecting area and high sensitivity. Its observations provide astronomers with a powerful tool for studying the distribution of hydrogen and, consequently, the structure and evolution of galaxies.

Known as FASHI DR2, the new dataset represents a dramatic expansion over FAST’s earlier observations. The telescope’s first dataset, released in January 2024, contained 41,741 detections and itself established a world record. The latest survey has increased that number to 156,411—almost four times the earlier FAST figure. According to the report, FAST has also surpassed the record of the US Arecibo Telescope’s ALFALFA survey, which had been a leading neutral-hydrogen survey for nearly two decades.

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