Webb captures a rare Einstein ring caused by light bending

A new image from the James Webb Space Telescope reveals a dazzling Einstein ring. At first glance, it appears to be a single, distorted galaxy.

But upon closer inspection, two galaxies appear: one in the foreground and another, much farther away, whose light bends around the closer galaxy to form a nearly perfect circle. This mesmerizing effect is known as an Einstein ring, a rare cosmic phenomenon.

How is an Einstein ring created?

The Einstein ring forms due to gravitational lensing. Light from a distant galaxy travels toward us but encounters a massive object on its path. That object, often another galaxy or a cluster of them, has enough mass to curve spacetime. As a result, the light bends around it.

From our perspective on Earth – or from a telescope like Webb – the light appears to wrap around the foreground object. If the alignment is just right, the bending of light forms a full circle.

When the alignment is not perfect, we may only see arcs or partial rings. These shapes aren’t artistic flourishes. They’re natural consequences of how gravity shapes the path of light across the universe.

This phenomenon doesn’t occur on smaller scales. Only when vast galaxies or clusters distort the path of light from extremely distant sources do we witness such rings.

Two galaxies, one illusion

What seems like a single, oddly-shaped galaxy is actually two galaxies far apart. The foreground galaxy sits at the center of the image. It is much closer to us.

It has a smooth, featureless structure with a bright core, which identifies it as an elliptical galaxy. This galaxy belongs to a larger cluster known as SMACSJ0028.2-7537.

The second galaxy, much farther away, lies directly behind the first. Its light, instead of coming straight to us, bends around the elliptical galaxy. That bending stretches the light into a ring.

This background galaxy is a spiral, and despite the distortion, its structure remains clear. We can see individual star clusters and gas formations. The bending doesn’t blur the image – it magnifies it.

Einstein rings allow scientists to observe galaxies too faint to detect otherwise. The lensing process acts as a cosmic magnifier. It brings hidden galaxies into view and lets astronomers study their structure and contents.

A global collaboration in space

​The image we now admire was made possible by the SLICE survey – Strong Lensing and Cluster Evolution. This program is led by Guillaume Mahler at the University of Liège in Belgium. He heads a team of international astronomers working to map galaxy clusters and their history.​

“Webb’s incredible resolution and sensitivity are a game changer for studying lenses like this,” noted Mahler.

​The SLICE survey uses the Near-Infrared Camera (NIRCam) on the James Webb Space Telescope. It targets 182 galaxy clusters to trace their development over eight billion years. These clusters are not chosen at random.​

Each one holds the potential to lens more distant galaxies. The information captured helps researchers understand how massive structures like clusters change with time.

In this case, the data from Webb was combined with observations from the Hubble Space Telescope. Hubble’s Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) added detail to the final image. The result is a layered, multi-spectrum look into the past.

Einstein rings and the early universe

Einstein rings do more than show pretty shapes. They unlock hidden data. Because the light from the background galaxy bends, we receive multiple paths of the same light.

Each path may take a different amount of time to arrive. By measuring those delays, astronomers can make precise calculations about mass, distance, and even dark matter distribution.

In essence, each Einstein ring becomes a tool. It helps map not just the light, but the invisible mass that shapes it. These measurements contribute to our broader understanding of gravity, dark matter, and the expansion of the universe.

Rings like these also allow us to look further into the past. The light from the lensed galaxy began its journey billions of years ago. When it finally reaches us, curved and magnified, it tells a story from the early universe. What we see is not just shape and color – it’s history, frozen in transit.

A spectacular cosmic coincidence

Astronomy is often about the unseen. Telescopes like Webb and Hubble don’t just capture light. They gather evidence from deep time and far space. Einstein rings act like windows, offering a clear line of sight into a universe we can’t reach otherwise.

This particular Einstein ring is rare for its clarity. Its near-perfect shape shows how well the two galaxies align. It is both a work of art and a valuable scientific record. Behind its glow lies a story of gravity, mass, light, and cosmic coincidence.

In looking at it, we’re not just staring at a circle. We are looking into a telescope made by nature, framed by chance, and captured by human curiosity.

Image Credit: ESA/Webb, NASA & CSA, G. Mahler

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