Two space telescopes, one “cosmic eye”: Hubble and Euclid captured a new, layered image of the Cat’s Eye Nebula
On 3 March 2026, ESA/Hubble published a new “Picture of the Month”: a detailed view of the Cat’s Eye Nebula (Cat’s Eye Nebula), also known as NGC 6543, created by combining observations from the NASA/ESA Hubble Space Telescope and the ESA Euclid telescope. It is one of the most recognizable planetary nebulae in the sky—the remnant of a Sun-like star that, in the final stage of its evolution, shed its outer layers of gas and dust. In the constellation Draco, at a distance of about 4,400 light-years according to measurements from ESA’s Gaia mission, the Cat’s Eye has served astronomers for decades as a kind of laboratory for understanding the “death” of intermediate-mass stars.
Why the Cat’s Eye is so important to astronomers
Planetary nebulae have a somewhat misleading name: they have nothing to do with planets, but in early telescopes, because of their roughly circular shape, they resembled tiny disks. Today it is clear that this is gas expanding into space, expelled from a star when it runs out of fuel for stable nuclear burning in its core. It was precisely in the case of the Cat’s Eye Nebula that, in the 19th century, it was confirmed that “planetary” nebulae are not stellar objects but gases: a 1864 analysis of the light spectrum revealed emission lines typical of tenuous, excited gas, not of stars or galaxies.
In modern astronomy, NGC 6543 is special because it is not a simple, uniformly expanding “sphere” of gas. On the contrary, in its interior and surrounding halo one can see concentric shells, high-velocity gas jets, density knots, and sequences of arcs and filaments. Such geometry suggests that the ejection of material was episodic: the central star did not “blow off” its outer envelope all at once, but through multiple pulses and changes in the stellar wind it left layer after layer of material. That is why astronomers often describe the Cat’s Eye as a “fossil record” of late evolutionary phases—traces that changes in the physics of a dying star imprint into the gas.
Hubble: sharpness at the very heart of the nebula
Hubble’s key contribution to the new composite image is its ability, in visible light, to resolve fine structures at the very center of the nebula. According to NASA’s description published on 3 March 2026, Hubble used the High Resolution Channel within the Advanced Camera for Surveys (ACS), optimized for extremely sharp images of a small field. It is precisely this “microscopic” precision that reveals layered bubbles and overlapping shells that create an eye-like impression, along with collimated jets and a network of tiny, compact knots shaped by shock waves. Such knots form when a faster, later stellar wind collides with slower material ejected earlier, compresses it, and “carves” it into complex shapes.
Hubble has not aimed its gaze at the Cat’s Eye for the first time. Its 1995 images were a turning point: they showed that what from the ground looks like a relatively regular nebula actually hides an extremely complex morphology. That example helped cement the idea that planetary nebulae often have a multilayered, asymmetric structure, in which magnetic fields, binary companions, or changes in the dynamics of the stellar wind play an important role. The newest processing goes a step further: NASA states that this release combines previously unused ACS data and modern image-processing techniques to produce the sharpest view to date.
Euclid: the wide frame that places the nebula in a “deep field”
While Hubble penetrates the center, Euclid brings breadth—and context. Euclid is primarily designed to map the distant Universe and study dark matter and dark energy by measuring the shapes and distances of galaxies. But in its deep imaging surveys it also records objects in our galactic neighborhood. In the wide view in visible and near-infrared light, the Cat’s Eye appears as a dazzling core immersed in a halo of colorful gas fragments “fleeing” from the central star. Especially prominent is a ring—the remnant of material ejected in an earlier phase, before the dominant central part of the nebula formed.
One of the most visually striking elements of Euclid’s frame is the background: a multitude of distant galaxies visible behind the nebula. The same image thus links two levels of the cosmos—the local, dramatic finale of a Sun-like star and the distant cosmic “wallpaper” of galaxies. ESA notes in its releases that such frames show how modern sky surveys simultaneously capture nearby astrophysical beauty and the farthest reaches of the observable Universe. Euclid’s deep fields, for example Deep Field North, were published in the first years of the mission as a demonstration of the telescope’s ability to record an enormous number of faint, distant galaxies in a single frame—and the Cat’s Eye appears in that mosaic as an unexpected “foreground.”
When “zoom” and “panorama” are combined: what scientists gain
It is precisely the combination of Euclid’s wide view and Hubble’s sharpness that makes this release more than just another pretty photograph. The wide frame helps reconstruct the history of material ejection: outer rings and fragments point to older episodes of mass loss, while inner shells and jets suggest later, more energetic phases. At the center, Hubble’s details make it possible to study shock fronts and dense knots—places where the physics of gas, radiation, and wind dynamics leaves its most readable signature.
Such “forensic” analysis matters because planetary nebulae represent the future of our own Sun, in terms of the general evolutionary scenario of intermediate-mass stars. Although the Sun will not explode as a supernova, in the distant future it will lose a significant fraction of its mass in the red-giant phase and then leave behind a hot core—a white dwarf—that will ionize the expelled gas and make it visible as a nebula. In that sense, the Cat’s Eye is not only a “cosmic eye” for observers on Earth, but also a reminder of universal stellar biology: stars recycle material, enrich interstellar space with heavier elements, and thus prepare the building material for new stars and planets.
From 19th-century spectroscopy to today’s space surveys
The story of the Cat’s Eye nicely shows how astronomy has advanced in technological leaps. The 1864 spectroscopy dispelled the misconception that planetary nebulae are “odd stars” and introduced gaseous physics into the interpretation of these objects. Hubble images from the late 20th century showed that nebular geometry can be extremely complex, often far from idealized spherical models. And now Euclid, an instrument designed for cosmology, in the same deep surveys records nearby objects as well and, as in this case, helps place them in a broader cosmic context.
Scientists remain cautious in their interpretations: although many structural elements are explained by episodic mass loss and interactions of stellar winds, the detailed cause of certain symmetries or jets is not always unambiguous. The literature discusses different scenarios—from the influence of a binary companion to changes in magnetic fields. What is certain, however, is that each new, more precise image like this one is used as a basis for testing models: where shock waves are expected, how density is distributed, how fast individual shells expand, and how radiation from the central star shapes the surrounding gas.
What exactly is seen in the new image
In the composite published on 3 March 2026, the left side shows Euclid’s wider frame in which the central nebula lies within an irregular, partially “cracked” ring of the outer halo. The colors in such renderings are not “photographic” in the sense of the human eye, but the result of mapping different wavelengths and intensities to highlight structures of gas and dust. The right side is Hubble’s close-up view of the heart of the nebula: layered, overlapping bubbles and arcs, framed by thin concentric circles and pierced by jets bursting out in opposite directions. At the center the star is visible—a hot core that still “lights up” the gas around it with radiative energy.
The bigger picture: Euclid’s mission and Hubble’s legacy
Euclid’s main task is not aesthetic, but measuring the large-scale structure of the Universe. Through extensive sky surveys, Euclid gathers data on galaxies and their shapes, enabling an indirect map of the distribution of dark matter (via gravitational lensing) and tracking how the expansion of the Universe accelerates because of dark energy. That is precisely why deep fields—multiple, repeated observations of the same areas—are crucial: they reveal the most distant, faintest galaxies and provide the statistics needed for precision cosmology. In that search, objects like the Cat’s Eye appear as a “bonus” and a reminder that within a single exposure local astrophysics and cosmology intertwine.
Hubble, on the other hand, has been building a legacy in the study of stellar life cycles for decades. Its ability to monitor objects over time, across different wavelengths, has enabled comparisons and measurements of changes on the scale of years or decades. For planetary nebulae, that means structures can be compared across multiple epochs, tiny shifts can be sought, and linked to expansion velocities. In the case of the Cat’s Eye, that has contributed to understanding how “young” such an object is on cosmic timescales and how quickly its structures change.
What this release means for the public and education
Space photographs often serve as a bridge between professional astronomy and the wider public. But in the case of the Cat’s Eye, that bridge has added value: it is an object historically linked to major scientific turning points—from early spectroscopic discoveries to the modern understanding of stellar winds. Today’s combination of Hubble and Euclid also shows how missions with different goals can complement each other: an instrument designed for cosmology provides the stage and background, while a telescope specialized for high resolution delivers the details that “tell” the story of gas physics.
At a time when space science increasingly relies on large datasets and automated analyses, visualizations like these remind us that astronomy remains a discipline in which the image often precedes the hypothesis. A view of the concentric shells, jets, and knots in the Cat’s Eye is not just an aesthetic experience; it is a map of processes that unfolded over thousands of years, whose traces are now read at a distance of several thousand light-years—at the moment when, from our perspective, those events are only now “arriving” to us at the speed of light.
Sources:- ESA/Hubble – official release “Two observatories, one cosmic eye” (3 March 2026.) (link)- NASA Science – article “Two Observatories, One Cosmic Eye: Hubble and Euclid View Cat’s Eye Nebula” (3 March 2026.) (link)- ESA/Euclid (Caltech) – “Euclid’s view of the Cat’s Eye Nebula” (19 March 2025.) (link)
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