JWST captures its most extreme gravitational lens ever

All throughout the Universe, gravity reigns supreme.

While the web of dark matter (purple, left) might seem to determine cosmic structure formation on its own, the feedback from normal matter (red, at right) can severely impact the formation of structure on galactic and smaller scales. Both dark matter and normal matter, in the right ratios, are required to explain the Universe as we observe it, with dark energy needed to explain how the expansion rate has evolved over time. Structure formation is hierarchical within the Universe, with small star clusters forming first, early protogalaxies and galaxies forming next, followed by galaxy groups and clusters, and lastly by the large-scale cosmic web.

Its unavoidable effects create massive, bound structures within our expanding Universe.

Most of the largest known galaxies in the Universe are found at the hearts of massive galaxy clusters, like the Hercules galaxy cluster shown here. Over time, galaxies within these clusters collide and merge, leading to bursts of new star-formation but making the galaxies more gas-poor, overall. After enough time has passed, most galaxies within such a cluster will become giant ellipticals, rather than disk-containing spirals.

JWST’s first science image unveiled a spectacular galaxy cluster.

This almost-perfectly-aligned image composite shows the first JWST deep field’s view of the core of cluster SMACS 0723 and contrasts it with the older Hubble view. Looking at the image details that are absent from the Hubble data but present in the JWST data shows us just how much discovery potential is awaiting scientists working with JWST.

With under a day of observations, impressive new features were revealed.

This NIRCam view of a selection of the gravitationally lensed region surrounding galaxy cluster SMACS 0723 contains multiple lensed galaxies, including the thrice-appearing Sparkler galaxy, highlighted here. The “sparkles” have been identified as star-forming knots of gas appearing atop already-existing globular clusters. Below the left-center of the second image of the Sparkler galaxy, a foreground star within the Milky way shows the characteristic diffraction spike pattern for JWST.

Many background objects get gravitationally lensed, enhancing and distorting their features.

Any configuration of background points of light, whether they be stars, galaxies, or galaxy clusters, will be distorted due to the effects of foreground mass via weak gravitational lensing. Even with random shape noise, the signature is unmistakable. The El Gordo galaxy cluster shows this effect (as do others) in a remarkably strong fashion, but large-area maps where mass, due to gravitational lensing, can be reconstructed to help understand the properties and distribution of dark matter on cosmic scales.

Now, JWST has set its sights on an already observed galaxy cluster: Abell S1063.

This Hubble image, first published in 2016, showcases galaxy cluster Abell S1063, with somewhere around one quadrillion solar masses, total. Behind this collection of around a thousand Milky Way-like galaxies, the light from even more distant objects gets bent, stretched, and magnified by gravitational lensing’s effects.

It observed for 120 hours across nine wavelength filters.

Preliminary total system throughput for each NIRCam filter, including contributions from the JWST Optical Telescope Element (OTE), NIRCam optical train, dichroics, filters, and detector quantum efficiency (QE). Throughput refers to photon-to-electron conversion efficiency. By using a series of JWST filters extending to much longer wavelengths than Hubble’s limit (between 1.6 and 2.0 microns), JWST can reveal details that are completely invisible to Hubble. The more filters that are leveraged in a single image, the greater the amount of details and features that can be revealed.

Inside and behind it, remarkable features were unveiled.

Imaged here in 9 different wavelength filters (from 0.9 to 4.8 microns) for a total of 120 hours, this JWST view of Abell S1063 is one of the most massive clusters ever imaged with deep field techniques. Many gravitationally lensed features can be clearly seen even with the naked eye.

Centrally spiked foreground galaxies, including cluster members, unveil active supermassive black holes.

This portion of the JWST image of Abell S1063 shows many white-appearing foreground galaxies that are members of the galaxy cluster itself: 4.7 billion light-years away. The redder, elongated galaxies are more distant, and are affected by the gravitation of the foreground cluster.

Behind them, galaxy shapes are bent and elongated by weak lensing.

This portion of JWST’s image of Abell S1063 shows mostly foreground cluster members, many of which exhibit JWST’s characteristic diffraction spike pattern around them. This pattern, visible in the infrared, is often indicative of an active supermassive black hole at the core of such a galaxy, but could also showcase strong central star-forming activity as an alternative explanation.

The more severe effects of strong lensing create arcs and multiple images.

In the upper left, foreground, gas-rich interacting galaxies rapidly form new stars throughout them, while streaked, mostly red background galaxies are distorted and magnified by the gravity of galaxy cluster Abell S1063, whose center is located to the lower-left of this image.

Many lensed galaxies are severely magnified as well, with gravity enhancing their light.

What appears to be two red, edge-on spiral galaxies parting ways with one another is actually two separate images of the same galaxy, induced because of the distortive effects of gravitational lensing. This galaxy, in reality, is smaller, fainter, and contains fewer stars than its appearance, which is enhanced via strong gravitational lensing.

Around individual galaxies, the same background features often appear multiple times.

This foreground galaxy, located around 4.7 billion light-years away, appears to have an active supermassive black hole. Around it, several features seem to appear multiple times: a trick of gravitational lensing, which bends light around this object via multiple paths to reach JWST’s watchful eye in several different locations.

A mix of undistorted foreground galaxies and lensed background galaxies appear simultaneously.

Foreground galaxies are undistorted in this image, while background galaxies are bent into arcs that appear to go around the foreground cluster’s center, which is off to the left of this image. Some objects, like the red irregular galaxies and the single arc with three bright spots, appear multiple times, while these lensed objects appear magnified and brightness-enhanced as well.

Lensing creates a preferred “orientation” for background galaxies by inducing shape noise.

While galaxies appear randomly oriented throughout space, gravitationally lensed galaxies are preferentially stretched into elliptical shapes along circles surrounding sources of mass. The red, background galaxies appear to be stretched horizontally here: evidence of gravitational lensing’s effects, not of the true underlying shapes of these background galaxies.

Redder colors indicate greater redshifts and distances.

In this image, different colors are assigned to different wavelengths. Violets and blues are assigned to wavelengths of 1.5 microns and under, greens to between 2 and 3 microns, yellow to between 3 and 4 microns, and oranges and reds to between 4 and 5 microns. The bright red galaxy just below the image’s center is much farther away than the foreground, white-appearing galaxy that it overlaps with.

Larger, longer streaks are more serendipitously aligned objects.

This portion of the JWST image of Abell S1063 appears to have rain-like streaks across it. These streaks are background galaxies stretched and brightness enhanced by gravitational lensing, with some non-parallel streaks further affected by the individual gravity of foreground galaxies in isolation.

Occasionally, radial arcs appear as well.

While most of the arcs created by gravitational lensing make circular shapes around the cluster’s center, some lensed arcs point radially away from the cluster’s center, like the faint red smudge below the right of center. Gravitationally lensed features enable astronomers to precisely map out the foreground cluster’s mass distribution.

Cosmic smash-ups showcase the violence of galaxy collisions.

Both foreground (right) and background (upper left) galaxy collisions and interactions can be seen in this image, with foreground galaxies unaffected by gravitational lensing and background galaxies greatly affected by it. Galaxy interactions are a primary cause of new star-formation throughout cosmic history, as this image showcases.

Lensing ultimately reveals small-scale features even at cosmological distances.

The longest, most stretched-out and feature-rich arcs in this image represent background galaxies that are most severely affected by the geometry of the foreground lens. Magnification and brightness enhancements can rise up to be hundreds or even thousands of times as severe as unlensed objects, revealing the sites of new star-formation even within galaxies located more than 10 billion light-years away.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words.