SPT-CL J0019-2026, a huge cluster of galaxies located 4.6 billion light-years away in the constellation of Cetus, has so much mass that it acts as a gravitational lens, causing light from extremely distant galaxies to bend around it.
Galaxy clusters contain thousands of galaxies of all ages, shapes and sizes. Typically, they have a mass of about one million billion times the mass of the Sun.
At one point in time galaxy clusters were believed to be the largest structures in the Universe — until they were usurped in the 1980s by the discovery of superclusters, which typically contain dozens of galaxy clusters and groups and span hundreds of millions of light-years.
However, clusters do have one thing to cling on to; superclusters are not held together by gravity, so galaxy clusters still retain the title of the biggest structures in the Universe bound by gravity.
Albert Einstein predicted in his theory of general relativity that massive objects will deform the fabric of space itself.
When light passes one of these objects, such as a galaxy cluster, its path is changed slightly.
Known as gravitational lensing, this effect is only visible in rare cases and only the best telescopes can observe the related phenomena.
“This new image from the NASA/ESA Hubble Space Telescope is populated with a serene collection of elliptical and spiral galaxies, but galaxies surrounding the central cluster SPT-CL J0019-2026 appear stretched into bright arcs, as if distorted by a gargantuan magnifying glass,” Hubble astronomers said in a statement.
“This cosmic contortion is called gravitational lensing, and it occurs when a massive object like a galaxy cluster has a sufficiently powerful gravitational field to distort and magnify the light from background objects.”
“Gravitational lenses magnify light from objects that would usually be too distant and faint to observe, and so these lenses can extend Hubble’s view even deeper into the Universe.”
This observation is…
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