Candidate Dark Galaxy-2 (CDG-2), an extremely faint galaxy, was discovered thanks to a dense cluster of globular clusters. This finding is significant for the study of dark galaxies and the nature of dark matter.

Features of CDG-2

Unlike most galaxies, which are identified by their starlight, gas emissions, and structure, CDG-2 contains almost no stars and has extremely low visible brightness. The main mass of this galaxy is made up of dark matter, which does not interact with light and can only be detected through its gravitational effects. Estimates suggest that about 99% of CDG-2’s mass is dark matter. The galaxy is classified as a low surface brightness object due to its faint glow.

Location and Conditions

CDG-2 is located in the Perseus Cluster, approximately 300 million light-years from Earth. This cluster experiences intense gravitational interactions, which cause galaxies to lose gas, especially hydrogen. The pressure of the surrounding medium also destroys smaller galaxies and hinders star formation. The lack of hydrogen, which is essential for star formation, may explain the absence of stars in CDG-2.

Detection Methods

To confirm the existence of CDG-2, data from three observatories were used:

• The Hubble Space Telescope provided high-resolution images that allowed the identification of four globular clusters.
• The Euclid Space Telescope confirmed the presence of faint diffuse light using wide-field images, which is especially important for finding galaxies with low surface brightness.
• The Subaru Telescope contributed additional supporting data from deep ground-based observations.

Combined observations showed that the globular clusters are located in a region of faint diffuse light, indicating the presence of an underlying galaxy.

Significance of the Discovery

Dark matter remains one of the main mysteries of modern physics. The discovery of CDG-2 advances the study of dark galaxies and helps deepen our understanding of the properties of dark matter.