In the vast tapestry of the universe, most galaxies shine brightly beyond cosmic time and space. However, a rare class of galaxies remains largely invisible. It is a galaxy with a low surface brightness, dominated by dark matter and only a sparse scattering of faint stars.

One such elusive object, called CDG-2, may be one of the most dark matter-rich galaxies ever discovered. (Dark matter is an invisible form of matter that does not reflect, emit, or absorb light.) A scientific paper detailing this discovery reads: Astrophysics Journal Letter.

Detecting such faint galaxies is extremely difficult. David Lee and his team at the University of Toronto in Canada used advanced statistical techniques to identify 10 previously identified galaxies with low surface brightness and two additional dark galaxy candidates by searching a tight group of globular clusters. Globular clusters are compact, spherical clusters of stars usually found orbiting around normal galaxies. These clusters may indicate the presence of subtly hidden stellar populations.

To confirm one of the dark galaxy candidates, astronomers used three observatories. hubble space telescopeESA (European Space Agency) Euclid space observatory and ground subaru telescope In Hawaii. High-resolution images from Hubble reveal four globular clusters clustered together in the Perseus galaxy cluster, 300 million light-years away. Subsequent follow-up studies using data from Hubble, Euclid, and Subaru revealed the presence of faint, diffuse light around the cluster. This is strong evidence for an underlying galaxy.

“This is the first galaxy detected solely in a population of globular clusters,” Lee said. “Under conservative assumptions, the four clusters represent the entire CDG-2 globular cluster.”

Preliminary analysis suggests that CDG-2 has the brightness of about 6 million Sun-like stars, with globular clusters accounting for 16% of its visible content. Remarkably, 99% of its mass appears to be dark matter, including both visible and dark matter. Much of the usual material that enables star formation (primarily hydrogen gas) is likely stripped away by gravitational interactions with other galaxies in the Perseus cluster.

Globular clusters have enormous stellar densities and are tightly bound together by gravity. This makes the galaxy cluster more resistant to gravitational tidal disturbances, thus making it a reliable tracker of such ghostly galaxies.

As exploration of the skies expands with missions like Euclid, NASA plans to Nancy Grace Roman Space Telescope,and Vera C. Rubin Observatoryastronomers are increasingly turning to machine learning and statistical methods to sift through vast datasets.

The Hubble Space Telescope has been in operation for more than 30 years and continues to make groundbreaking discoveries that shape our fundamental understanding of the universe. Hubble is an international cooperation project between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages telescope and mission operations. Denver-based Lockheed Martin Space also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.