Galaxies are filled with dark matter, a mysterious substance that greatly surpasses the mass of stars, planets, and moons combined—by about five times. However, some galaxies are so dominated by dark matter that it’s astonishing. Recently, astronomers using the Hubble and Euclid Space Telescopes found one of the most dark-matter-heavy galaxies known, dubbed CDG-2.
CDG-2 is located approximately 245 million light-years away. Unlike typical galaxies that shine brightly across the universe, dark galaxies like CDG-2 are nearly invisible. They consist of only a few stars, hidden by an overwhelming amount of dark matter, which makes up about 99% of the galaxy’s mass, compared to the usual five-to-one ratio seen in other galaxies.
Dark matter is elusive—it doesn’t interact with light the way normal matter does. But astronomers have confirmed its presence through its gravitational effects on visible matter. This is how they identified CDG-2; the galaxy revealed itself through faint glows around clusters of stars known as globular clusters.
The discovery started when a team studied these clusters, which can hint at nearby hidden galaxies. From this investigation, they identified ten dim galaxies, including two candidates for dark galaxies. Observations from Hubble and other telescopes showed a faint light near these clusters, indicating a ghostly galaxy nearby. The team’s leader, David Li from the University of Toronto, noted that this was the first galaxy found by examining just the globular clusters surrounding it.
CDG-2 has a brightness equivalent to about six million stars similar to our Sun. Yet, most of this light isn’t from stars shining brightly but from ancient clusters that survived gravitational interactions with neighboring galaxies, which likely stripped away much of the original star content.
This research offers insight into how dark matter shapes our universe. According to a recent study, about 85% of the total mass in the universe is dark matter, influencing the structure and behavior of galaxies like CDG-2.
For those curious about dark matter’s broader implications, the community is buzzing with discussions on social media platforms. Many are fascinated by the idea that most of our universe consists of something we can’t see. Scientists continue to explore this enigma, seeking to unlock the full story of dark matter in the cosmos.
Research findings were published in The Astrophysical Journal Letters. As our tools and understanding improve, we get closer to grasping the intricate dance between dark matter and visible stars.
