(ORDO NEWS) — Hubble has provided an image of the galaxy cluster Abell 611, located at a distance of about 3.2 billion light-years from Earth. The existence of this cluster is a mystery to astronomers.
In particular, its “web” of rapidly rotating galaxies does not seem to have enough mass to prevent the cluster from breaking apart.
This is a well-known problem with massive structures such as galaxies and galaxy clusters. One gets the impression that they simply do not have enough total mass to remain intact.
Interestingly, this problem does not arise on smaller cosmic scales. No additional mass is required to explain the integrity of the solar or other star-planetary systems. So why is this rule being violated on a large scale?
The prevailing theory is that the universe contains a vast amount of matter known as dark matter.
This unknown quantity does not interact with light: it does not emit, reflect or absorb any part of the electromagnetic spectrum. This quality makes dark matter incredibly difficult to study.
However, dark matter is easily quantifiable. In fact, clusters of galaxies such as Abell 611 are ideal laboratories for quantifying dark matter, thanks to the abundant evidence of gravitational lensing visible within the cluster.
One example of lensing is clearly visible in the center of the image, to the left of the cluster’s glowing core, where the light curve is visible.
This curve represents light from a more distant source that has been warped and distorted by the huge mass of Abell 611.
From the way the light has been bent by the cluster, its true mass can be measured. The results can be compared with the estimate of its mass obtained from all visible components of the cluster.
The difference between calculated and observed mass is striking. Astronomers have calculated that approximately 85% of the matter in the universe is dark matter.
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