At a Glance: Gravitational Lensing

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What is a gravitational lens? What does it do?

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

Rotating planet with atmosphere, galaxies in space as backdrop. Text, at a Glance. A warped point of view.
The sky with stars and yellow disks of light.
Text, a cluster of galaxies can act like a giant lens in space.
Gravitational lensing. A giant lens in space between us and a distant source of light would bend and focus that light, allowing us to see it better. Diagram, earth, hypothetical glass lens in space, distant source of light.
Like a lens, a cluster's gravitational force can concentrate the light from an even-farther galaxy, magnifying it.
Diagram, distant galaxy, galaxy cluster, Hubble.
But depending on how these gravitational lenses are shaped, our views of the faraway galaxies can become distorted.
When a gravitational lens has a smooth, spherical shape, we might see a ring of light.
Image, distant, lensed object.
Text, If the gravitational lens is elongated, we sometimes see multiple, evenly spaced projections of the distant galaxy. Image, distant, lensed object.
Text, When the gravitational lens is clumpy and uneven, as galaxy clusters are, we often see the more distant galaxies as smeared arcs or streaks of light. Image, gravitational lens.
Images of galaxies.
Such gravitational arcs are common features in hubble images of the most massive galaxy clusters.