Light does not constantly take a trip in straight lines. As Einstein anticipated in his Theory of General Relativity, enormous items will warp the material of area itself. When light passes among these enormous items, such as a cluster of galaxies, its course is altered somewhat.
This result, called gravitational lensing, is just noticeable in uncommon cases and just the very best telescopes can observe the associated phenomena.
Hubble’s level of sensitivity and high resolution permit it to see faint and far-off gravitational lenses that can not be discovered with ground-based telescopes whose images are blurred by the Earth’s environment. The gravitational lensing leads to numerous pictures of the initial galaxy each with a typically distorted banana-like shape or perhaps into rings.
Hubble was the very first telescope to solve information within these numerous banana-shaped arcs. Thanks to its sharp vision, it can expose the shape and internal structure of the lensed background galaxies straight. In by doing this one can quickly match the various arcs originating from the exact same background things– be it a galaxy or perhaps a supernova– by eye.
Gravitational lensing can be utilized to ‘weigh’ clusters since the quantity of lensing depends upon the overall mass of the cluster. This has actually considerably enhanced our understanding of the circulation of the ‘hidden’ dark matter in galaxy clusters and for this reason in the Universe as a whole. The result of gravitational lensing likewise enabled an initial step towards exposing the secret of the dark energy.
As gravitational lenses work as zoom glasses it is possible to utilize them to study far-off galaxies from the early Universe, which otherwise would be impossibly faint to see due to their country mile from Earth.
The post on the structure of the Universe has more information on Hubble’s deal with dark matter.
“When we first observed the galaxy cluster Abell 2218 with Hubble in 1995 we mainly aimed at studying the cluster and its galaxies. But we got a surprise. The images showed dozens and dozens of gravitationally lensed arcs. When we showed these ultrasharp images to our colleagues they could immediately see the importance of using gravitational lensing as a cosmological tool.”
— Richard Ellis, Astronomer, University of Cambridge and California Institute of Technology