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In new images from the NASA/ESA/CSA James Webb Space Telescope to celebrate its fourth science anniversary, a familiar galaxy transforms into something far richer, and far more complex, than ever seen before. Webb’s unprecedented sensitivity across near- and mid-infrared wavelengths cuts through the thick lanes of dust that obscure Centaurus A’s centre in visible light, showing a densely packed tapestry of individual stars and an active, everchanging galaxy. These images mark four years of better-than-anticipated performance and successful science operations for the most powerful space telescope in history.
Centaurus A (also known as NGC 5128) is 11 million light-years away from Earth, relatively close in cosmic terms. Yet, unlike most nearby galaxies, it is very active, making it a powerful laboratory for understanding how galaxies and black holes grow and evolve together.
At its core sits a supermassive black hole actively feeding on surrounding material. As it does, the black hole launches powerful jets and releases enormous amounts of energy, shaping the galaxy around it. At the same time, Centaurus A bears the scars of a dramatic past: a major collision with another galaxy roughly two billion years ago. The aftermath of that merger is still visible today in its unusual structure and ongoing star formation.
Visible light observations from the NASA/ESA Hubble Space Telescope could not reveal the central region where dust blocked the view, while NASA’s retired Spitzer Space Telescope revealed large scale structures in the infrared without resolving individual stars. Now, Webb brings both clarity and depth, exposing the galaxy’s inner workings star by star.
Dust, awe
Webb’s mid-infrared vision highlights the galaxy’s rich dust structures, which glow in intricate shapes that surprise and even perplex astronomers. A warped, parallelogram-like band cuts across the galaxy’s centre, while wisps of material stretch outward like cosmic clouds.
An “S” shaped feature, most notable in the image from Webb’s MIRI (Mid-Infrared Instrument), is also unusual and invites questions that need further study to answer. What created this shape? How does the black hole influence it? Is it influenced by merger-induced star formation?
Many of the glowing red points in the MIRI image are dust-rich stars or stellar nurseries, where aging stars are shedding material back into space or new stars are forming. This dust is the raw ingredient for future generations of stars and planets, making it central to the ongoing life cycle of the galaxy.
Written in its stars
With Webb’s high resolution, astronomers can now study Centaurus A star by star, even in its long-obscured central region. What looks “grainy” in the image from Webb, most obvious in the combined MIRI and NIRCam (Near-Infrared Camera) view, is actually a densely packed field of individual stars, together carrying information about the galaxy’s past.
With Webb’s view of Centaurus A, it becomes a case of galactic archaeology. Each star revealed helps to reconstruct when different events happened: when older stars first formed, when activity slowed down, a burst of star formation during the collision, and stars born from gas stirred in its aftermath. Together, they form a timeline of the galaxy’s evolution.
Dynamic black hole
Webb’s capabilities go beyond imaging. By analysing light with spectroscopy, astronomers can measure how gas moves within the galaxy.
Early findings from Webb show fast-moving ionised gas flowing outward, likely driven by the black hole’s activity, and warmer molecular hydrogen in a warped rotating disk near the centre. These observations help explore one of astronomy’s biggest questions: How does a black hole influence an entire galaxy?
The answer appears to be complex. The black hole can trigger star formation by compressing gas, but also limit it by pushing material away. Centaurus A offers a rare, nearby view of this cosmic interplay.
By tracing dust in never-before-seen detail, resolving millions of stars, and revealing the motion of gas near a supermassive black hole, Webb transforms Centaurus A into a vivid record of cosmic history.
Another incredible year of science and imagery
The fourth year of Webb’s science operations has delivered further groundbreaking science and discoveries from places across the Universe. Astronomers found new evidence for a planet orbiting Alpha Centauri, just four light-years away from our Sun. Webb showcased eight spectacular gravitational lenses out of an in-depth survey that identified hundreds of candidates. By looking into the cradles of star clusters in nearby galaxies, scientists found that more massive clusters emerge faster; meanwhile in our own Solar System, Webb mapped the upper atmosphere and auroras of Uranus.
In the early Universe, Webb revealed a black hole that formed before its galaxy did, providing new evidence for how supermassive black holes originated, and identified a supernova occurring just 730 million years after the Big Bang — the earliest to date. Researchers presented the strongest evidence yet that some of the “little red dots” discovered by Webb in 2022 are in fact "black hole stars". Webb also took a fresh look at the Hubble Ultra Deep Field, resulting in a new view that reveals thousands of distant galaxies dating back to the earliest periods of cosmic history.
Among the unique images produced by Webb over the last year were the gossamer nebulae around a planet-forming disc, intricate details in the edge of the Helix Nebula, the complex heart of a cosmic butterfly and young stars across every stage of formation. Webb highlighted a beacon of light in the swirls of galaxy Messier 77, and details of the stellar lifecycle in galaxy NGC 5134. Webb and Hubble also joined forces to share the most comprehensive view of Saturn to date, showing layers and storms in its atmosphere.
[Image description: A horizontal image of the galaxy Centaurus A stretches across a black background filled with thousands of tiny purple, pink, and white points of light. The galaxy is brightest at its centre, where a brilliant white and pale pink glow radiates outward. Eight diffraction spikes extend from the central glow. Delicate loops and wispy ribbons of pink and lavender arc above and below the centre of the image in the shape of an ‘S’. A band of gray and white dust in the shape of a parallelogram cuts across the middle of the galaxy. Mottled patches and bright knots are scattered throughout the dusty band. The galaxy’s outer edges fade into soft, cloud-like plumes with feathery textures that stretch toward the left and right sides of the image. Against the surrounding darkness, a few bright foreground stars shine with Webb’s distinctive diffraction spikes, while countless fainter stars create a speckled backdrop.]
Credits: NASA, ESA, CSA, STScI. Image Processing: A. Pagan (STScI), J. Depasquale (STScI), M. Garcia Marin (ESA Office at STScI); CC BY 4.0
