Focusing in on Gravitational Lenses

Gravity acts as a lens, magnifying and distorting space and time in a way that is similar to an optical lens like those in eyeglasses or contact lenses. As light passes through a gravitational lens, it may take different paths, producing multiple images of the same object. When that light emerges from the lens, we see several contorted images of a single object. Gravitational lenses help boost our view, allowing Hubble to capture faint, distant objects.

This illustrations reveals how an Einstein Cross forms. In the upper-left corner is a quasar. Is its light travels toward Hubble (lower-right corner), it passes a large galaxy. The gravity from the galaxy bends warps the quasar's light like a lens, creating four bright versions of it that Hubble sees.

This graphic illustrates how a faraway quasar (an extremely bright region in the center of some distant galaxies) is altered by a massive foreground galaxy. The galaxy's powerful gravity warps and magnifies the quasar's light, producing four distorted images of the quasar. Dark matter is an invisible substance that makes up the bulk of the universe's mass and creates the scaffolding upon which galaxies are built. Quadruple images of a quasar rare because the background quasar and foreground galaxy require an almost perfect alignment.

NASA, ESA, and D. Player (STScI)

Einstein Cross G2237+0305
NASA, ESA, and J. Lotz and the HFF Team (STScI)
Five months after its April 1990 launch, Hubble captured four gravitationally lensed images of quasar G2237+0305. Called an Einstein Cross, the image reveals a distant quasar gravitationally lensed four times by a relatively nearby galaxy (visible as bright smudge at the center of the cross).

Spots of light that are galaxies in this image. Some of the galaxies appear to be stretched due to gravitational lensing. Three very bright orange spots of light near the center in a row.

This Hubble Space Telescope image, taken in 1994, shows several blue, loop-shaped objects that actually are multiple images of the same galaxy. The "gravitational lens" created by the cluster of yellow, elliptical and spiral galaxies — called 0024+1654 — near the photograph's center magnified and distorted the light from the distant galaxy. Though the gravitational light-bending process was well known, Hubble's high resolution revealed structures within the blue-shaped galaxy that astronomers had never seen before.

W.N. Colley and E. Turner (Princeton University), J.A. Tyson (Bell Labs, Lucent Technologies), and NASA

Supernova Refsdal and Galaxy Cluster MACS J1149.6+2223
NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)
The enormous galaxy cluster MACS J1149.6+2223, located more than 5 billion light-years away, creates a gravitational lens that facilitated two of Hubble’s most exciting discoveries using gravitational lenses. The first was Supernova Refsdal. Hubble captured the supernova because the gravitational lens created by a massive galaxy embedded in MACS J1149.6+2223 bent and magnified its light. Refsdal is some 4.3 billion light-years farther than MACS J1149.6+2223 or 9.3 billion light-years from Earth.
Icarus (MACS J1149+2223 Lensed Star 1)
NASA, ESA, and P. Kelly (University of Minnesota)
First discovered in 2014, astronomers calculated how Refsdal’s light might move through MACS J1149.6+2223’s enormous gravitational lens and predicted its reappearance. While looking for and finding the supernova’s reappearance in MACS J1149.6+2223, they also found an enormous, distant, blue star they nicknamed Icarus.
Icarus is so far away that its light took 9 billion years to reach Earth. Because the star’s light had such a long distance to travel, Hubble's observations captured the star as it appeared when the universe was about 30 percent of its current age.

In this video, Dr. Brian Welch explains the science in Hubble's image of the gravitationally lensed supernova Rafsdal.

NASA's Goddard Space Flight Center; Producer: James Leigh

Earendel
NASA, ESA, Brian Welch (JHU), Dan Coe (STScI); Image Processing: Alyssa Pagan (STScI)
Just four years after the discovery of Icarus, Hubble broke its own record by finding a more distant star, called Earendel, in a gravitational lens created by a huge galaxy cluster called WHL0137-08. The star sits in a ripple of spacetime (indicated by the dotted line) that produces extreme magnification, allowing Earendel to stand out against its host galaxy, which appears as a red arc. It took Earendel’s light 12.9 billion years to reach Earth, traveling at 186,000 miles per second (300,000 km per second). Hubble’s image captured the star as it appeared when the universe was only seven percent of its current age – within the first billion years after the universe’s birth in the big bang – making it the most distant individual star ever seen.

In this video, Dr. Brian Welch explains Hubble's image of the gravitationally lensed star Earendel.

NASA's Goddard Space Flight Center; Producer: James Leigh

Learn More

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