NASA’s James Webb Space Telescope has captured new infrared images of the nebula nicknamed the “Exposed Cranium,” revealing layered structures that earlier observatories could only hint at. NASA says the object lies about 5,000 light-years away in the constellation Vela, and Webb’s data show a striking vertical dark lane and multiple distinct regions within the surrounding gas and dust. The findings offer a rare, high-resolution window into the final stages of a star still actively reshaping its surroundings.
A Brain-Shaped Nebula Gets a Sharper Look
The nebula earned its macabre nickname after scientists using NASA’s Spitzer Space Telescope noted its resemblance to an exposed brain. That earlier infrared portrait, taken by NASA’s Spitzer observatory, established the nebula’s basic shape. Webb’s instruments bring a different order of detail. Both its Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) pick up a distinctive dark lane running vertically through the nebula’s center, splitting it into what looks like left and right hemispheres and reinforcing the brain-like appearance.
What makes this dark lane scientifically interesting, rather than just visually striking, is the disagreement between the two cameras about how it appears. According to Webb mission scientists, the lane is more noticeable in NIRCam’s view, yet its structural details are seen more clearly through MIRI. That tension is not a contradiction but a clue: NIRCam captures shorter-wavelength near-infrared light, which is more easily blocked by dust, while MIRI’s longer mid-infrared wavelengths can penetrate deeper into the same material. The fact that both instruments register the lane differently tells astronomers something about the dust density and temperature gradient along that divide, and helps constrain models of how opaque the central structures really are.
Twin Jets and a Wolf-Rayet Heart
Webb’s resolution has allowed researchers to propose that the vertical dark lane is not simply a shadow or a chance alignment of dust. Instead, it could be related to an outflow from the central star. Such outflows typically occur as twin jets bursting out in opposite directions, carving channels through the surrounding gas. If confirmed, this would mean PMR 1’s symmetrical appearance is not the product of uniform expansion but of directed, high-energy ejections that sculpted the nebula from the inside out, with the dark lane tracing where material has been cleared or compressed.
The star at the center of PMR 1 is no ordinary dying sun. Peer-reviewed spectroscopy published in the Monthly Notices journal classified it as a Wolf-Rayet-type central star, with possible designations of [WO4] or [WC4]. These classifications indicate an extremely hot, compact remnant that has shed its hydrogen envelope and now drives fierce stellar winds rich in carbon and oxygen. Optical emission lines detected in the nebula trace those winds as they slam into slower-moving gas expelled during earlier phases of the star’s life. That collision zone is where much of the nebula’s visible structure originates, and it is exactly the kind of environment where twin-jet outflows would leave their mark in the form of cavities, knots, and sharp-edged filaments.
Layers of a Star’s Life History
Beyond the dark lane, Webb’s images show that PMR 1 contains distinct regions capturing different phases of its evolution. The nebula’s outer shell consists of gas blown off by earlier stellar winds and subsequently shocked by faster winds from the central star. Closer in, the inner regions are rich in dust and molecules, material that has not yet been fully processed by the star’s radiation. This layered architecture acts as a time capsule: each zone records a different episode of mass loss, from the gentle shedding of the star’s outer atmosphere to the violent, fast winds of its current Wolf-Rayet phase, allowing astronomers to reconstruct a rough timeline of the star’s late-life outbursts.
Joseph Hora, principal investigator for Spitzer’s earlier observations, noted that such images are used to “understand stars’ mass loss history and evolution,” as described in Spitzer-era releases from Caltech. Webb now extends that work with far greater sensitivity. Where Spitzer could outline the nebula’s general shape, Webb resolves the boundary between the shocked outer shell and the dusty interior, giving astronomers a way to measure how much material was lost at each stage and how quickly the central star’s wind speed changed over time. By comparing PMR 1 to other planetary nebulae in current Webb observations, researchers can test whether its layered structure is typical or the result of unusually violent mass loss.
Why Asymmetry Matters for Stellar Death Models
Most textbook descriptions of planetary nebulae present them as roughly spherical shells, expanding evenly away from a dying star. PMR 1 undercuts that simplicity. The vertical lane, the apparent twin-jet geometry, and the contrast between its hemispheres show that even a seemingly symmetric nebula can hide complex, directional flows. In general, astronomers use structures like these as inputs for computer simulations to explore how asymmetries in stellar outflows can grow into large-scale features like the ones Webb now resolves. PMR 1 therefore becomes a key test case for models that try to explain why many planetary nebulae exhibit bipolar lobes, rings, or hourglass shapes instead of uniform bubbles.
The Exposed Cranium also highlights how multi-wavelength observations change the story. In optical light, much of the dust that shapes the dark lane would be nearly invisible, while in mid-infrared it dominates the scene. By tying together Webb’s infrared views with earlier optical spectra and images, scientists can estimate how much of the nebula’s apparent symmetry is an illusion created by viewing angle and how much reflects genuine physical alignment. Those insights feed back into broader theories of stellar death, including how mass loss from stars like PMR 1 enriches the interstellar medium with carbon, oxygen, and heavier elements that later generations of stars and planets inherit.
Webb in a Growing Landscape of NASA Observatories
PMR 1 is only one example of how Webb is transforming planetary nebula studies, and its observations are part of a larger tapestry of missions overseen by NASA’s space science program. While Webb peers into the infrared, other observatories focus on X-rays, ultraviolet, or radio waves, each revealing different pieces of the puzzle. Together, they show how dying stars like PMR 1 contribute to the cosmic cycle of matter, returning processed gas and dust to space where it can form new generations of stars. Updates on such cross-mission results frequently appear across NASA news releases, which track discoveries from Webb as well as from older observatories still operating in orbit.
For readers who want to follow how the Exposed Cranium fits into Webb’s broader science portfolio, NASA maintains curated summaries of recently published findings and features that highlight key images and papers. Short-form explainers and video segments on platforms like NASA+ streaming walk through Webb images in accessible language, while long-form interviews on NASA podcasts often bring mission scientists together to compare objects such as PMR 1 with other planetary nebulae. These resources, alongside the main NASA portal, give the public a way to see how a single, brain-shaped nebula observed by Webb can ripple outward into improved models of stellar evolution, better simulations of galactic chemistry, and a richer understanding of how stars like our Sun will eventually end their lives.
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*This article was researched with the help of AI, with human editors creating the final content.
