"Dark Galaxy" CDG-2 Detected in Perseus | Hubble Space Telescope

"Dark Galaxy" CDG-2 Detected in Perseus | Hubble Space Telescope

The NASA/European Space Agency Hubble Space Telescope has revealed an exceptional discovery in the Perseus galaxy cluster—CDG-2, an ultra-low surface brightness galaxy composed of 99% dark matter.

This elusive galaxy remained hidden until astronomers detected a slight increase in globular cluster density, suggesting the presence of an underlying galactic structure. 

Observations from Hubble, European Space Agency's Euclid observatory, and the Subaru Telescope confirmed a faint halo of diffuse light surrounding these ancient star clusters.

Analysis indicates CDG-2 has the luminosity of approximately six million Sun-like stars with the clusters comprising about 16% of its visible matter. The galaxy's normal matter was likely stripped away through gravitational interactions within the Perseus cluster.

This discovery provides a rare opportunity to study dark matter's fundamental properties and how it shapes galactic evolution across the universe.

Credit: NASA's Goddard Space Flight Center 
Paul Morris: Lead Producer
Video Credits:
A simulation of the formation of dark matter structures from the early universe until today.
Ralf Kaehler/SLAC National Accelerator Laboratory, American Museum of Natural History
Image of the Subaru Telescope: NAOJ via ESA
Duration: 2 minutes, 36 seconds
Release Date: Feb. 17, 2026

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