NASA's Hubble Identifies One Of Darkest Known Galaxies

Rare low-surface-brightness galaxy CDG-2 is dominated by dark matter and contains only a sparse scattering of stars.

Published on Feb. 23, 2026

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Astronomers have identified one of the darkest known galaxies in the universe using data from the Hubble Space Telescope, the Euclid space observatory, and the Subaru Telescope. The galaxy, dubbed CDG-2, is a rare low-surface-brightness galaxy that is dominated by dark matter and contains only a sparse scattering of faint stars.

Why it matters

Detecting such faint and dark galaxies is extremely challenging, but studying them can provide valuable insights into the nature of dark matter and the early formation of galaxies in the universe.

The details

Using advanced statistical techniques, a team led by David Li of the University of Toronto identified CDG-2 by searching for tight groupings of globular clusters, which can signal the presence of a faint, hidden stellar population. Hubble's high-resolution imaging revealed a close collection of four globular clusters in the Perseus galaxy cluster, 300 million light-years away. Follow-up studies using Hubble, Euclid, and Subaru data then revealed a faint, diffuse glow surrounding the star clusters, providing strong evidence of an underlying galaxy.

  • The science paper detailing this finding was published in The Astrophysical Journal Letters.

The players

David Li

A researcher at the University of Toronto, Canada, who led the team that identified CDG-2.

Hubble Space Telescope

NASA's space observatory that provided high-resolution imaging to reveal the globular clusters in CDG-2.

Euclid

The European Space Agency's space observatory that contributed data to the study of CDG-2.

Subaru Telescope

The ground-based telescope in Hawaii that also provided data for the analysis of CDG-2.

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What they’re saying

“This is the first galaxy detected solely through its globular cluster population.”

— David Li, Researcher, University of Toronto (The Astrophysical Journal Letters)

What’s next

As sky surveys expand with missions like Euclid, NASA's upcoming Nancy Grace Roman Space Telescope, and the Vera C. Rubin Observatory, astronomers are increasingly turning to machine learning and statistical methods to sift through vast datasets to identify more of these elusive dark galaxies.

The takeaway

The discovery of CDG-2, one of the darkest known galaxies in the universe, highlights the power of combining data from multiple observatories and advanced analytical techniques to uncover the secrets of the cosmos, even in the faintest and most elusive celestial objects.