Astronomers have identified a possible “dark galaxy” located about 300 million light-years from Earth. The object, known as CDG-2, appears to contain very few stars but a large amount of dark matter.
Researchers believe it could belong to a rare group of galaxies known as dark galaxies. These galaxies are extremely faint and may contain little visible light.
The discovery used observations from the Hubble Space Telescope, the Euclid Space Telescope, and the Subaru Telescope in Hawaii. Scientists published the findings in The Astrophysical Journal Letters.
A Galaxy Dominated by Dark Matter
CDG-2 lies inside the Perseus Cluster, a massive group that contains thousands of galaxies.
Scientists say the galaxy is extremely faint. Its brightness is only about 0.005% of the Milky Way’s brightness. In comparison, the Milky Way shines about 20 billion times brighter than the Sun.
Researchers believe most of the galaxy’s mass comes from Dark Matter, an invisible substance that does not emit light but influences objects through gravity.
Because CDG-2 contains very few stars, scientists describe it as an “almost-dark galaxy.”
Scientists Found It Through Globular Clusters
Astronomers used an unusual method to locate the faint galaxy. Instead of searching for bright stars, they looked for Globular Clusters.
Globular clusters are dense, spherical groups of very old stars. These clusters often remain visible even when the surrounding galaxy is extremely faint.
Researchers discovered four globular clusters grouped together in the Perseus Cluster. Further observations revealed a faint halo around them. This glow suggested the presence of a hidden galaxy.
Scientists believe the clusters remain bound together by gravity created by dark matter in the galaxy.
Why the Galaxy Has So Few Stars
Astronomers think CDG-2 once had the material needed to create more stars. However, nearby larger galaxies may have stripped away its hydrogen gas early in its history.
Without that gas, the galaxy could not continue forming new stars. It likely remained with only its dark matter halo and a few star clusters.
Scientists describe this result as the “skeleton” of a galaxy that failed to grow normally.
A New Way to Find Hidden Galaxies
Researchers say using globular clusters could become a new way to discover dark galaxies. Many more of these faint objects may exist across the universe.
Future observations with the James Webb Space Telescope could help confirm how much dark matter CDG-2 contains.
Studying such galaxies may help scientists understand how dark matter behaves in space. Because these galaxies contain little normal matter, they offer a clearer view of dark matter’s effects.
