Astronomers discover hidden 'dark galaxy' anchored by star clusters

Astronomers have identified a faint object that, while barely visible, is holding a compact group of star clusters together, indicating the presence of a hidden galaxy that nearly disappears into space.

The discovery began with four globular clusters—dense groups of stars—located unusually close to one another within the Perseus galaxy cluster, 300 million light-years away. While such clusters normally orbit within galaxies and tend to drift apart over time, this specific group remained tightly bound, implying a strong gravitational pull.

The team wondered if a random alignment was possible, but statistical tests showed it to be highly unlikely, suggesting that a massive, unseen object is anchoring them.

Researchers now consider this object, named Candidate Dark Galaxy-2 (CDG-2), to be potentially one of the most dark matter-dominated galaxies ever discovered. Dark matter is an elusive substance that does not emit light but exerts a powerful gravitational force.

“This is the first galaxy detected solely through its globular cluster population,” said David Li, an astrostatistics researcher at the University of Toronto and the study’s lead author.

Published in The Astrophysical Journal Letters, these findings raise questions about how many other faint galaxies exist, as many could be too dim to detect with existing methods.

Overlooking objects like this could lead to wildly incorrect estimates of the total number of galaxies in the universe. However, the new technique developed by the team may help uncover more galaxies that are currently hidden from view.

Researchers examined images of CDG-2 captured by NASA’s Hubble Space Telescope, the European Space Agency’s Euclid space observatory, and the Japanese Subaru Telescope in Hawaii. Initially, they found no obvious signs of a galaxy. The area appeared almost empty, containing only the clusters themselves.

While CDG-2 seems to possess only four globular clusters, the Milky Way has over 150. The mysterious object shines dimly, emitting the light of only 6 million suns—a mere fraction compared to the billions of suns illuminating our own galaxy.