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Globular clusters are ancient groups of hundreds of thousands, even millions of stars, gravitationally bound in a single structure from about 100 to 200 light years away. These objects are thought to be among the oldest stellar structures in the universe. Globular clusters are the favorite targets of amateur astronomers. We know that 150 to 180 clusters of this type exist around our Milky Way. At the naked eye, they appear as fuzzy stars. Through a small telescope, they separate to form glittering islands of innumerable snowball-shaped stars. The NASA / ESA Hubble Space Telescope is so powerful that it can see globular clusters at 300 million light-years away. Looking at the heart of the Coma group – a huge structure of more than a thousand gravity-bound galaxies – Hubble captured 22,426 globular groups.
This Hubble mosaic is part of the Coma group of more than 1,000 galaxies, located 300 million light-years away from Earth. Image Credit: NASA / ESA / J. Mack, STScI / J. Madrid, Australian Telescope National Facility.
"Because globular clusters are much smaller than entire galaxies, they provide a better understanding of how the tissue of space is deformed by the gravity of the Coma cluster," said Dr. Juan Madrid of the Australian Telescope National Facility and its co-authors.
"In fact, Coma's group is one of the first places where the observed gravitational anomalies were seen as revealing an invisible mass in the Universe, later called" Dark Matter. "
At the distance of Coma's group, his globular groups appear as points of light, even for Hubble's clear vision.
The study revealed 22,426 globular clusters dispersed in the space between galaxies. They are orphaned from their original galaxy because of near-collisions inside the traffic-jammed cluster.
Hubble revealed that some globular clusters align along bridge-shaped patterns. This is the revealing proof of the interactions between galaxies where they shoot each other gravelly against each other as if they were shooting.
"I first thought about the distribution of globular clusters in Coma when I was examining Hubble images that show the globular clusters extending up to the edge of the globe. a given photograph of galaxies in the cluster of Coma, "said Dr. Madrid.
"I was looking forward to having more data from one of the former Hubble surveys designed to obtain data on the entire Coma cluster, called the Coma Cluster Treasury Survey."
"However, in the middle of the program, in 2006, Hubble's Advanced Camera for Surveys (ACS) had an electronic failure."
The incredible clarity of Hubble was used to perform a complete census of the smallest members of the Coma cluster: 22,426 globular clusters (circled in green). Image Credit: NASA / ESA / J. Mack, STScI / J. Madrid, Australian Telescope National Facility.
To fill in the gaps in the investigation, Dr. Madrid and his colleagues have painstakingly drawn numerous images of Hubble's cluster of galaxies from Hubble's various observing programs. They were able to assemble a mosaic of the central region of the cluster.
They then developed algorithms to scan images of the Coma mosaic containing at least 100,000 potential sources.
The program used the color of globular clusters (dominated by the glow of aging red stars) and the spherical shape to eliminate superfluous objects – mainly bottom galaxies not associated with Coma agglomeration.
"One of the interesting aspects of our research is that it presents the astonishing science that will be possible with NASA's future wide-field infrared surveyor telescope (WFIRST), which will have a much wider field of view than Hubble, "said Dr. Madrid.
"We will be able to image clusters of whole galaxies at a time."
The results are published in the Astrophysical Journal.
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Juan P. Madrid et al. 2018. Wide-field map of intracluster global clusters in coma. ApJ 867, 144; doi: 10.3847 / 1538-4357 / aae206
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