Think you can spot a gravitational lens?

Introduction by Andrew Grant
Image captions by Sebastian Fernandez-Mulligan

One afternoon, Michael Gladders had his astronomy students at the University of Chicago sift through thousands of sky survey images. The assignment was to find examples of gravitational lensing, in which light from an astronomical object is warped and magnified when it is deflected by a galaxy cluster or other massive object. In the case of strong gravitational lensing, the visual markers include rings or arcs of light that surround the foreground cluster.

The catch of the exercise, Sebastian Fernandez-Mulligan writes in the cover story for Physics Today‘s March issue, was that the students should take only two seconds to view each image. That way, the students would build intuition when it comes to spotting lenses—just as seasoned astronomers have in the nearly half century since the discovery of the first strong gravitational lens. The role of intuition in the discovery and identification of gravitational lenses is the focus of Fernandez-Mulligan’s story.

Inspired by Gladders’s classroom exercise, Physics Today asked Fernandez-Mulligan to choose six deep-sky images. Of those images, which were taken by the Hubble and Euclid space telescopes, only some contain arcs or other signatures of a strong gravitational lens. See if you can spot those signatures during the three seconds (we give you an extra second) that each image appears in the animated slideshow below. Then scroll down to see how you did.

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