00:00Across the universe, galaxies shine like scattered jewels, vast collections of stars lighting the
00:07darkness. But hiding among this brilliance are ghosts, galaxies so faint they nearly vanish into
00:15the void. These are low surface brightness galaxies, collections of dim stars dominated
00:21almost entirely by dark matter. Dark matter is a mysterious, invisible substance that makes up the
00:28bulk of our universe. Astronomers studying the Perseus galaxy cluster found one of the darkest yet,
00:35a faint smudge known as CDG2. Detecting it was like spotting a black cat in a coal bin.
00:42Scientists uncovered CDG2 not by its light, but by its companions, ancient globular clusters.
00:50These densely packed spherical star groupings typically orbit larger galaxies.
00:56Researchers found a small increase in the density of these clusters,
01:00suggesting the existence of an underlying faint galaxy pulling them together.
01:05Using NASA's Hubble Space Telescope, ESA's Euclid Observatory, and the Subaru Telescope in Hawaii,
01:13astronomers confirmed CDG2's faint halo of diffuse light surrounding four of these compact globular
01:19clusters. Preliminary analysis suggests CDG2 has the luminosity of roughly 6 million sun-like stars,
01:29with the clusters comprising about 16 percent of its visible matter. The galaxy's total mass,
01:35including both visible and dark matter, is overwhelmingly dominated by dark matter,
01:40which is 99 percent of the total. Much of CDG2's normal matter, primarily hydrogen gas, was likely
01:49stripped away by gravitational interactions within the Perseus cluster. Globular clusters are more
01:55resistant to such disruption because they are so densely packed together and gravitationally balanced.
02:01With the ongoing efforts of Hubble and companion observatories, such as Webb and the upcoming
02:07Roman Space Telescope, astronomers will continue uncovering these hidden realms,
02:12galaxies made not of what we can see, but of what holds the universe together.
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