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Astronomy & Astrophysics 101: Gravitational Lensing

GAL-CLUS-022058s

NASA/ESA Hubble Space Telescope image of GAL-CLUS-022058 in the southern hemisphere constellation of Fornax (The Furnace). Image Credit: ESA/Hubble & NASA, S. Jha, Credit: L. Shatz

Gravitational lensing occurs when a massive celestial body—like a galaxy cluster—causes enough warping of spacetime that the path of light around it is bent as seen through a lens. The body that bends the light is accordingly called a gravitational lens.

According to Einstein’s general theory of relativity, time and space merge into one entity known as space-time. Within this theory, massive objects cause spacetime to warp, and gravity is simply the warp of spacetime. As light travels through spacetime, theory predicts that light’s path is also curved by an object’s mass. Gravitational lensing is a dramatic and observable example of Einstein’s theory in action. Extremely massive celestial bodies such as galaxy clusters cause a significant curvature of space-time. So they act like gravitational lenses. When light from a more distant light source passes through a gravitational lens, the light path is bent and a distorted image of the distant object—perhaps a ring or halo around the gravitational lens—can be observed.


Gravitational lensing occurs when a massive celestial body—like a galaxy cluster—causes enough warping of spacetime that the path of light around it is bent as seen through a lens. The body that bends the light is accordingly called a gravitational lens. Photo credit: ESA/Hubble (M. Kornmesser & LL Christensen)

An important consequence of this lens distortion is the magnification that allows us to observe objects that would otherwise be too far away and too faint to see. Hubble uses this magnifying effect to study objects that would otherwise be beyond the sensitivity of its 2.4 meter diameter primary mirror, showing us the most distant galaxies mankind has ever encountered.


This Space Sparks episode explores the concept of gravitational lensing. This effect is only visible in rare cases and only with the best telescopes – including the[{” attribute=””>NASA/ESA Hubble Space Telescope — can observe the results of gravitational lensing. The strong gravity of a massive object, such as a cluster of galaxies, warps the surrounding space, and light from distant objects traveling through that warped space is curved away from its straight-line path. This video highlights how Hubble’s sensitivity and high resolution allow it to see details in these faint, distorted images of distant galaxies.

Hubble’s sensitivity and high resolution allow it to see faint and distant gravitational lenses that cannot be detected with ground-based telescopes whose images are blurred by the Earth’s atmosphere. The gravitational lensing results in multiple images of the original galaxy each with a characteristically distorted arc-like shape or even into rings. Hubble was the first telescope to resolve details within these multiple arc-shaped features. Its sharp vision can reveal the shape and internal structure of the lensed background galaxies directly.

Word Bank Gravitational Lensing

Credit: ESA/Hubble & NASA, S. Jha, Acknowledgement: L. Shatz

An image released in 2020 as part of the ESA/Hubble Picture of the Week series of the object known as GAL-CLUS-022058s revealed the largest ring-shaped lensed image of a galaxy (known as an Einstein ring) ever discovered, also one of the most complete. The near exact alignment of the background galaxy with the central elliptical galaxy of the cluster warped and magnified the image of the background galaxy into an almost perfect ring.

Learn more about Hubble’s observations of gravitational lensing here.

https://scitechdaily.com/astronomy-astrophysics-101-gravitational-lensing/ Astronomy & Astrophysics 101: Gravitational Lensing

Tom Vazquez

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