Hubble Discovers Largest Known Group of Star Clusters, New Clues into Dark Matter

NASA's Hubble Space Telescope has discovered a population of an estimated 160,000 globular star clusters -- the largest such grouping ever discovered.

Globular clusters, considered the windows into early galaxy formation, are comprised of hundreds of thousands of stars, all tightly packed around one another. According to a new study based on the recent images, these formations are also beneficial in revealing new insights into dark matter, described as "the invisible gravitational scaffolding on which galaxies are built."

The study reveals that the majority of the globular clusters in Abell 1689, as the grouping is called, formed near the center where a massive reservoir of dark matter is located. As one moves farther out from this center, the globular clusters become more and more sparse, correlating with a drop in the amount of dark matter.

"We show how the relationship between globular clusters and dark matter depends on the distance from the center of the galaxy grouping," Karla Alamo-Martinez of the Center for Radio Astronomy and Astrophysics of the National Autonomous University of Mexico in Morelia said in a statement. "In other words, if you know how many globular clusters are within a certain distance, we can give you an estimate of the amount of dark matter."

Ninety-five percent of globular cluster formation is estimated to have occurred within the first 1 billion to 2 billion years following the birth of the universe, with current formations containing some of the oldest known surviving stars.

"The globular clusters are fossils of the earliest star formation in Abell 1689, and our work shows they were very efficient in forming in the denser regions of dark matter near the center of the galaxy cluster," Blakeslee said. "Our findings are consistent with studies of globular clusters in other galaxy clusters, but extend our knowledge to regions of higher dark matter density."

In all, Hubble was able to identify the visible-light glow of 10,000 globular clusters, which Blakeslee's team estimates represents one-sixteenth of the total population.

"Even though we are looking deep into the cluster, we're only seeing the brightest globular clusters, and only near the center of Abell 1689 where Hubble was pointed."