Insight Into: Gravitational Lensing

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What is gravitational lensing? How does it help Hubble see farther than it normally could?

Frontier Fields
Produced by the Space Telescope Science Institute’s Office of Public Outreach.
All images, illustrations, and videos courtesy of NASA except:
·       Gravitational lensing animations courtesy of G. Bacon & F. Summers (STScI) and NASA, ESA & L. Calçada
·       Taurus constellation drawing from Firmamentum Sobiescianum sive Uranographia by Johannes Hevelius, courtesy of the United States Naval Observatory
·       Hubble orbit animation courtesy of G. Bacon (STScI)
·       Hubble Space Telescope slewing animation courtesy of ESA/Hubble (M. Kornmesser & L. L. Christensen)
·       Simulation of a lens passing over the Hubble Deep Field courtesy of ESA/Hubble (M. Kornmesser & L. L. Christensen)
·       Background star field courtesy of A. Feild (STScI)
·       Frontier Fields background star field images courtesy of the Digitized Sky Survey
·       Chandra spacecraft illustration courtesy of Northrop Grumman Corporation
·       Animation of the Hubble Space Telescope flying over Earth courtesy of ESA/Hubble (M. Kornmesser)
Written by Vanessa Thomas
Designed by Marc Lussier 
Music courtesy of Associated Production Music

Floating through space, surrounded by glowing stars and spinning galaxies.
Like the words in a history book, galaxies narrate the story of the universe.
Yet, even with the Hubble Space Telescope, there are some galaxies that are too faint and far away to see.
On occasion, though, nature lends a hand to help us to understand some of these otherwise invisible galaxies.
Light usually travels along straight paths.
However, the gravity of a massive object warps the space around it.
As light passes the object, it curves to follow the warped space.
Clusters of galaxies are the most massive objects in space.
Illustration of Hubble in space collecting data from a distant galaxy.
With its enormous gravitational field, a galaxy cluster can act like a gigantic lens to redirect and magnify light from an even farther galaxy behind the cluster.
This trick of nature called gravitational lensing, allows us to find faraway galaxies we could never see otherwise, and to glimpse once-secret chapters of the universe's early history.