Astronomers using Hubble Space telescope images of the Coma galaxy cluster some 300 million light years away have identified a staggering 22,426 globular clusters in a survey aimed at learning more about the distribution of matter and dark matter in the huge grouping of more than 1,000 galaxies.
Globular clusters contain some of the oldest stars in the universe, and about 150 are known to orbit the core of the Milky Way. Some of those are visible to the naked eye as fuzzy “stars,” but at the Coma galaxy cluster’s distance, globulars are little more than points of light even to the Hubble Space Telescope.
But Juan Madrid of the Australian Telescope National Facility in Sydney, Australia, led a team of researchers, including students, that searched through archived Hubble imagery to assemble a mosaic of the central region of the Coma cluster. They developed an algorithm to scour the mosaic’s 100,000 potential sources, relying on the colour and spherical shape of globular clusters to eliminate background galaxies and other “extraneous” objects.
The team found Coma globulars scattered throughout the space between the cluster’s galaxies, apparently orphaned by gravity-driven near-collisions inside the grounded assembly. the Hubble data revealed some of the globulars lined up in bridge-like patterns, clear evidence of gravitational interactions between galaxies.
“One of the cool aspects of our research is that it showcases the amazing science that will be possible with NASA’s planned Wide Field Infrared Survey Telescope that will have a much larger field of view than Hubble,” said Madrid. “We will be able to image entire galaxy clusters at once.”