FAST and Arecibo Reveal Possible Dark Galaxy AGC 322753 with 2 Billion Solar Masses of Hydrogen

Astronomers using the Five-hundred-meter Aperture Spherical Telescope (FAST) and the Arecibo Observatory have identified a massive reservoir of neutral hydrogen, designated AGC 322753, that appears to lack any detectable starlight. The object contains roughly 2 billion times the mass of the Sun in hydrogen gas, a potential fuel for future star formation. Radio observations indicate the gas may be organized in a rotating disk, yet deep optical imaging shows no corresponding galaxy. This unusual combination suggests AGC 322753 could be a 'dark galaxy'—a system dominated by dark matter and gas but with few or no stars. Such objects are predicted by galaxy formation models but have been difficult to confirm. The discovery, made possible by combining the sensitivity of FAST with Arecibo's legacy data, offers a rare opportunity to study how galaxies form and why some fail to ignite star formation. If confirmed, AGC 322753 would be one of the most extreme examples of a starless galaxy, challenging our understanding of the baryon cycle and the role of dark matter in shaping cosmic structures. The findings could help explain the missing satellite problem and the nature of low-surface-brightness galaxies. Future observations with next-generation telescopes, such as the James Webb Space Telescope, may reveal faint stellar populations or further confirm the object's dark nature.