Astronomers using NASA/ESA’s Hubble Space Telescope have identified a rare cosmic phenomenon: a galaxy almost entirely dominated by dark matter. This mysterious object is named Candidate Dark Galaxy-2 (CDG-2).
In contrast to galaxies in general which shine brightly with billions of stars, CDG-2 appears very dim and almost transparent. Findings published in The Astrophysical Journal Letters This states that the “ghost” galaxy is located in the Perseus galaxy cluster, about 300 million light years from Earth.
Extreme Composition: 99 Percent Dark Matter
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The most surprising thing for researchers is the mass composition. The dark matter in CDG-2 accounts for up to 99 percent of its total mass. This ratio is considered very extreme because in standard galaxies, dark matter usually accounts for only five times more than ordinary matter.
Visually, CDG-2 only has four globular clusters. For comparison, the Milky Way Galaxy has more than 150 such clusters.
The light from CDG-2 is very faint, only equivalent to the light of 6 million Sun-like stars, where 16 percent of the brightness comes from the globular cluster within it.
CDG-2 Galaxy Key Statistics
- Nama: Candidate Dark Galaxy-2 (CDG-2)
- Location: Perseus Galaxy Cluster
- Distance: 300 Million Light Years
- Composition: 99% Dark Matter
- Number of Globular Clusters: 4
Detection Method: Tracking Unseen Traces
Dark matter does not reflect, emit, or absorb light, making it impossible to see directly. The research team led by David Li from the University of Toronto, Canada, had to use advanced statistical techniques.
“This is the first galaxy detected solely through its population of globular star clusters,” said David Li in his official statement. The team looked for tight clustering of globular star clusters as a marker for the existence of stellar populations hidden beneath the darkness.
To confirm these findings, astronomers mobilized the power of three observatories at once:
- Hubble Telescope: Reveals high-resolution images of a collection of star clusters.
- Euclid Telescope (ESA): Confirmed the presence of very faint diffuse (scattered) light around the object.
- Subaru Telescope (Hawaii): Provides supporting data to validate the galaxy’s environment.
Why is CDG-2 Lacking Stars?
Scientists theorize that the lack of stars in CDG-2 is caused by the extreme environment in the Perseus cluster. Much of the normal material such as hydrogen gas, which is the raw material for star formation, has likely been “stripped away” due to gravitational interactions with neighboring, more massive galaxies.
However, CDG-2’s globular star cluster is able to survive because it has a very large star density and is tightly bound gravitationally. This resistance to tidal gravitational disturbances is what makes the cluster a reliable “footprint” for astronomers to recognize this nearly invisible galaxy.
The discovery of CDG-2 opens a new chapter in our understanding of how dark matter shapes the structure of the universe and how galaxies can survive despite losing almost all their normal matter. (Z-10)
