Over 800 dark galaxies have been revealed by a team of American and Japanese astronomers using the Subaru Telescope located at the Mauna Kea Observatory, Hawaii.
The 854 ‘ultra-dark’ galaxies, as they have been named by the astronomers are located in the Coma Cluster of the Berenice’s Hair Constellation. They are part of a rich galaxy cluster which is comprised of thousands of systems.
However, unlike the brighter brethren in the Coma Cluster, these 854 galaxies were hard to spot until recently. Now, they come to add to the potential of dark matter study which already received a boost with the discovery of 47 dwarf dark galaxies during the previous year.
The Mauna Kea Subaru Telescope, measuring 8.2 meters in length was the key to unlocking the gate to these previously hidden dark galaxies. Thus, it provided scientists with the opportunity to observe the 854 ultra-dark galaxies which are approximately 300 million light years away from our home planet.
These ultra-dark Coma Cluster galaxies were observed to have a similar spatial distribution to the more luminous galaxies found here, and to contain some of the oldest stellar populations, albeit scarce.
The binding force behind the dim old stars is thought to be dark matter. To this extent, further research will shed new light on understanding dark matter.
“Not only these galaxies appear very diffuse, but they are very likely enveloped by something very massive,”
stated Jin Koda, Stony Brook University New York astrophysicist.
Visible matter or stars in the case of the ultra dark galaxies is estimated at one percent of the mass of each of 854 galaxies. The rest of 99 percent is accounted for by dark matter. At the same time, the rate of visible matter of the ultra dark galaxies fares well below the average fraction across the universe. So the glue that holds visible matter together in a galaxy is something unseen.
And it is not the gravitational force, which, due to the location of the ultra dark galaxies near the center of the Coma Cluster, is so strong that it could have well destroyed them by now. Nonetheless, the extremely powerful gravitational force is thought to account for the low density of the old ultra dark galaxies at the heart of the Coma Cluster.
The 854 ultra dark galaxies are observed to be of a similar size to our Milky Way. Nonetheless, the proportion of stars in each of them is approximately 1 over 1000 compared to our galaxy.
At this point, 1,000 galaxies in the Coma Cluster have been identified. This, together with the Leo Cluster form the Coma Supercluster.
The detailed findings of the astronomers will be comprised in a paper published in the Astrophysical Journal Letters, the journal of the American Astronomical Society, come June 24th.
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