Astronomers have discovered a remarkable faint galaxy. They call it CDG-2. This object sits in the Perseus galaxy cluster. It lies 300 million light-years from Earth.
Researchers believe CDG-2 consists almost entirely of dark matter. In fact, 99% of its total mass comes from dark matter. Only a tiny fraction appears as visible stars.
A team led by Dayi (David) Li from the University of Toronto made the find. They used data from three powerful telescopes. Hubble provided sharp images. Euclid added wide-field views. Subaru contributed deep observations.
The team did not search for stars at first. Instead, they looked for globular star clusters. These bright, spherical groups orbit galaxies. The researchers spotted four dense clusters in the Perseus area.
Next, they combined images from Hubble, Euclid, and Subaru. This revealed a faint glow around the clusters. The glow signaled a hidden galaxy.
Analysis shows CDG-2 produces starlight equal to just six million suns. About 16% of that light comes from its globular clusters. The rest hides in dark matter.
Li explains this marks a breakthrough. Astronomers found the galaxy purely through its globular clusters. No one had discovered a galaxy this way before.
Scientists think CDG-2 lost most of its gas long ago. Gravitational interactions inside the dense Perseus cluster stripped the material away. As a result, only dark matter and star clusters remain.
This object may rank as the most dark-matter-dominated galaxy known. It offers fresh clues about galaxy formation. It also highlights dark matter’s dominant role in the universe.
Future telescopes will hunt for more such objects. NASA’s Roman Space Telescope will scan wide areas. The Vera C. Rubin Observatory will provide deep surveys. These tools could reveal additional dark galaxies soon.
The discovery excites the astronomy community. It proves creative methods uncover hidden cosmic secrets. CDG-2 opens new doors to understanding the invisible universe.
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