Bold opening: What if the universe hides in plain sight, revealed only by the faintest glimmers of starlight and a clever eye? That’s essentially what NASA’s Hubble Space Telescope helped us uncover with one of the darkest galaxies ever found. And this is the part most people miss: you can detect a galaxy not by bright flames of stars, but by the ghostly footprint they leave behind in globular clusters.
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Across the vast expanse of the cosmos, most galaxies blaze brilliantly across billions of years and light-years. Yet a rare category remains almost invisible—low-surface-brightness galaxies that are dominated by dark matter and host only a sparse sprinkling of faint stars.
One such elusive object, named CDG-2, may be among the most dark matter–dominated galaxies ever found. (Dark matter is an unseen form of matter that does not reflect, emit, or absorb light.) The research paper detailing this discovery appeared in The Astrophysical Journal Letters (https://iopscience.iop.org/article/10.3847/2041-8213/adddab/meta).
Detecting these faint galaxies is extraordinarily challenging. Using advanced statistics, David Li of the University of Toronto and his team validated 10 previously confirmed low-surface-brightness galaxies and identified two additional dark-galaxy candidates by searching for tight groupings of globular clusters—dense, spherical star clusters that typically orbit normal galaxies. These clusters can signal the presence of a hidden, faint stellar population.
To confirm one of the dark-galaxy candidates, astronomers combined data from three observatories: NASA’s Hubble Space Telescope, ESA’s Euclid space observatory, and the ground-based Subaru Telescope in Hawaii. Hubble’s sharp imaging revealed a close-knit quartet of globular clusters in the Perseus galaxy cluster, about 300 million light-years away. Subsequent analyses using Hubble, Euclid, and Subaru data uncovered a faint, diffuse glow surrounding the clusters—clear evidence of an underlying galaxy.
“This is the first galaxy detected solely through its globular cluster population,” Li said. “Under conservative assumptions, the four clusters make up the entire globular cluster population of CDG-2.”
Early analyses suggest CDG-2 has the luminosity of roughly 6 million Sun-like stars, with the globular clusters contributing 16% of its visible matter. Remarkably, about 99% of its total mass—including both visible matter and dark matter—appears to be dark matter. It’s likely that much of its normal matter necessary for star formation—principally hydrogen gas—was stripped away by gravitational interactions with other galaxies inside the Perseus cluster.
Globular clusters are incredibly dense and gravitationally bound, which makes them unusually resistant to tidal disruption. As a result, they serve as reliable tracers for uncovering these ghostly galaxies.
As sky surveys grow with missions like Euclid, NASA’s upcoming Nancy Grace Roman Space Telescope, and the Vera C. Rubin Observatory, researchers are increasingly turning to machine learning and advanced statistics to sift through colossal datasets.
Hubble has operated for more than three decades and continues to drive groundbreaking discoveries that deepen our understanding of the universe. Hubble is a collaborative project between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland manages the telescope and mission operations. Lockheed Martin Space, based in Denver, supports operations at Goddard. The Space Telescope Science Institute in Baltimore, operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
Related visuals and videos
- Dark Galaxy CDG-2 Near Perseus Cluster – An image of the low-surface-brightness galaxy CDG-2 dominated by dark matter with few stars.
- “Dark Galaxy” Identified by Hubble (Video) – CDG-2, one of the most dark-matter–dominated galaxies discovered.
- Dark Galaxy Near Perseus Cluster (Compass Image) – Hubble ACS image with Euclid data, featuring reference markers.
Explore more topics
- Hubble’s Star Clusters – Clues to stellar lifecycles
- AI and Hubble Science – How machine learning accelerates discovery
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Last Updated: Feb 18, 2026
Editor: Andrea Gianopoulos
Location: Public Release. This material from the originating organization may reflect point-in-time information and has been edited for clarity, style, and length. Mirage.News does not endorse any positions; all views are those of the authors. View the full article here: https://www.miragenews.com/nasas-hubble-identifies-one-of-darkest-known-1622094/
