Galaxies Billions of Years Old: 8 Examples of Gravitational Lensing | Webb Telescope
COSJ100013+023424
The foreground galaxy whose gravity is bending the light from more distant objects is seen as it was when the Universe was 6.4 billion years old. The more distant lensed galaxy, appearing as an arc, was invisible in previous NASA/European Space Agency Hubble Space Telescope observations and has now been revealed by Webb’s sensitive infrared eyes. This discovery is crucial for studying star formation in distant galaxies.
COSJ100024+015334
Nicknamed ‘the COSMOS-Web Ring’, this lensing system contains a massive elliptical galaxy that acts as the gravitational lens and a more distant star-forming galaxy whose light has been stretched into a perfect circle. The lensed galaxy gives us a glimpse of galactic life when the Universe was just over a billion years old.
COSJ100018+022138
Previously confirmed using data from the NASA/European Space Agency Hubble Space Telescope, this lens is revealed in greater detail by Webb. The elliptical lensing galaxy is seen as it was when the Universe was about 4 billion years old. The blue galaxy whose light has been warped into a circle goes back even further, shown as it was when the Universe was less than 2 billion years old.
COSJ100024+021749
The light from the luminous blue foreground galaxy traveled for about 4 billion years to reach us, while the background galaxy’s light has been on a much longer journey, taking more than 11 billion years to reach us. This newly detected lens will help researchers understand galaxy evolution and the formation of stars in dusty environments.
COSJ095914+021219
The golden galaxy at the center of the image is an elliptical galaxy whose immense gravity is bending the light from a more distant galaxy. The background galaxy is faintly visible as a golden arc along the top of the foreground galaxy.
COSJ100025+015245
Somewhat resembling a ringed planet at first glance, this lens is markedly different from the others presented in the Picture of the Month compilation of gravitational lenses from the COSMOS-Web survey. This shows a rare case in which the lensing galaxy is a thin disc galaxy rather than a giant elliptical galaxy. The dust within the disc absorbs the source’s light, providing a valuable opportunity to study dust in very distant galaxies.
COSJ095921+020638
An elliptical galaxy roughly 6 billion light-years away is bending the light from a more distant galaxy whose light has been stretched into a delicate circle. The blue points of light along the circle may be individual star clusters.
COSJ095593+023319
The glowing elliptical galaxy at the center of this image is about 8.6 billion light-years away. This gravitational lens is ideally suited for the study of dark matter, an invisible form of matter that makes up most of the mass in the Universe.
This James Webb Space Telescope picture shows eight stunning examples of gravitational lensing. Gravitational lensing, first predicted by Einstein, occurs because massive objects like galaxies and clusters of galaxies dramatically warp the fabric of spacetime. When a massive foreground object lines up just so with a background galaxy, the light from the background galaxy bends as it navigates the warped spacetime on its way to our telescopes.
Depending on how perfect the alignment is, the light from the background galaxy can be bent into an arc, a circle (a phenomenon called an ‘Einstein ring’) or even split into multiple images.
Arcs and circles are prevalent in these gravitationally lensed galaxies. They were identified in data from COSMOS-Web, a 255-hour Treasury program (#1727). COSMOS-Web aims to understand the formation of the most massive galaxies in the Universe, identify galaxies that were present when the first stars and galaxies reionized the Universe’s hydrogen gas, and study the relationship between the mass of a galaxy’s stars and the mass of its galactic halo across cosmic time.
Using these data, researchers carried out the COSMOS-Web Lens Survey, or COWLS, to search for gravitational lenses. The researchers inspected more than 42,000 galaxies by eye and picked out more than 400 promising lensing candidates. This picture feature presents a collage of eight of the most spectacular lenses identified by the research team.
This collection of gravitational lenses spans an incredible range of cosmic history. The background galaxies, whose shapes appear visibly distorted, let us peek all the way back to when the Universe was barely more than a billion years old.
These images demonstrate Webb’s ability to uncover and reveal never-before-seen details in gravitationally lensed galaxies. These discoveries open a unique window into the early days of the Universe and enable the study of exquisite details within distant galaxies like individual star clusters and supernovae.
From top-to-bottom: COSJ100013+023424, COSJ100024+015334, COSJ100018+022138, COSJ100024+021749, COSJ095914+021219, COSJ100025+015245, COSJ095921+020638, and COSJ095593+023319.
Image Credits: ESA/Webb, NASA & CSA, G. Gozaliasl, A. Koekemoer, M. Franco
Release Date: Sept. 30, 2025
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