The James Webb Space Telescope has captured a detailed infrared portrait of a dying star’s ghostly remains: a planetary nebula nicknamed the “Exposed Cranium” for its skull-like silhouette. The new image of PMR 1, released by NASA from observations taken in late March 2025, combines near- and mid-infrared data to reveal layered shells of gas and dust that older telescopes could only hint at. For astronomers studying how Sun-like stars end their lives, the observation provides a clearer view of a complex, multi-layered laboratory for stellar death.
From Spitzer’s Sketch to Webb’s Portrait
PMR 1 first appeared in infrared more than a decade ago, when NASA’s now-retired Spitzer Space Telescope captured it at wavelengths of 3.6, 4.5, and 8.0 micrometers, rendered in blue, green, and red, according to the Spitzer observation record. Scientists working with Spitzer data coined the “Exposed Cranium” label because the nebula’s lobed structure resembled the top of a skull. That early view established the basic outline: a compact cloud of ionized gas surrounded by a cooler outer shell where hydrogen molecules glow in infrared light. But Spitzer’s resolution left the finer architecture of those shells largely unresolved.
Webb’s observation, taken in late March 2025, represents a generational leap. The telescope trained two instruments on PMR 1 simultaneously. Its Near-Infrared Camera, or NIRCam, applied filters designated F150W, F187N, F444W, and F470N, while the Mid-Infrared Instrument, or MIRI, targeted longer wavelengths that trace warm dust. The result is a composite that separates the nebula’s components by temperature and composition in a way Spitzer never could. NIRCam data emphasize background stars and distant galaxies shining through and around the nebula, while MIRI data emphasize dust threaded through the expanding shell. The pairing turns a single object into two complementary maps, one of stellar light and one of dusty debris.
Anatomy of a Stellar Corpse
Planetary nebulae form when a star roughly the mass of the Sun exhausts its nuclear fuel, swells into a red giant, and then sheds its outer layers into space. The exposed core, now a hot compact remnant, bathes the ejected gas in ultraviolet radiation, causing it to fluoresce. PMR 1 fits this template but adds a twist: its central star has been classified as Wolf-Rayet–type in published survey work (see MNRAS). Wolf-Rayet stars drive exceptionally fast, dense stellar winds, and those winds can slam into the slower-moving material ejected earlier. That collision can sculpt asymmetric lobes, compressed rims, and shock-heated filaments, all features that planetary nebula researchers look for when testing models of late-stage stellar evolution.
Webb’s dual-wavelength view of PMR 1 sharpens the picture of this interaction. The nebula’s outer hydrogen-rich shell appears as a distinct boundary in the infrared data, separating the hot ionized interior from the cooler molecular envelope. Inside that boundary, the gas glows because the hot central remnant is still energetic enough to strip electrons from atoms. Outside, hydrogen molecules survive intact and radiate at longer wavelengths. The clean separation visible in the new image suggests that the shell boundary is sharper than earlier, lower-resolution data implied, raising questions about how quickly winds from the central star are eroding the outer molecular layer.
What Two Instruments Reveal Together
Most coverage of new Webb images focuses on visual spectacle, but the scientific value of the PMR 1 observation lies in how NIRCam and MIRI data complement each other. NIRCam’s shorter-wavelength filters pick up emission from ionized gas and from stars both within and behind the nebula, effectively providing a census of the stellar neighborhood. MIRI’s longer wavelengths, by contrast, trace warm dust grains that absorb starlight and re-emit it in the mid-infrared. Dust production in planetary nebulae matters because those grains eventually mix into the interstellar medium and seed the formation of new stars and planets.
The observation was carried out under JWST Proposal 9224, with M. Garcia Marin listed as principal investigator. While the full scientific analysis from that program has not yet been published, the public release of the composite image already highlights structural details that were invisible to Spitzer. The dust distribution, in particular, appears clumpy rather than smooth, which could be consistent with instabilities driven by collisions between a fast stellar wind and the outer shell. If confirmed by spectral analysis, that clumpiness could help explain why planetary nebulae across different surveys show such varied shapes, even when their central stars have similar masses.
In addition to morphology, the combined dataset is expected to refine estimates of the nebula’s age and expansion rate. By comparing the size of the ionized cavity to the thickness of the molecular shell, astronomers can infer how long ago the red giant phase ended and how rapidly the fast wind has been reshaping the surroundings. Follow-up spectroscopy with Webb should also reveal the chemical fingerprints of elements such as carbon, nitrogen, and oxygen in both gas and dust, constraining how efficiently the dying star enriched its environment.
PMR 1 in the Broader Catalog
PMR 1, also cataloged as PN G272.8+01.0, sits in the southern constellation Vela at an estimated distance of approximately 5,000 light-years. It was one of several planetary nebulae that Spitzer grouped together in a set illustrating the final stages of stellar aging. That earlier Spitzer set placed PMR 1 alongside other dying stars to show the range of morphologies that planetary nebulae can exhibit, from nearly spherical shells to highly elongated, bipolar structures. Webb’s new view now anchors PMR 1 more firmly within that menagerie, revealing it as neither perfectly round nor strongly bipolar, but instead as a layered, somewhat asymmetric bubble with subtle protrusions and knots.
This intermediate appearance makes PMR 1 especially useful for testing theories about how planetary nebula shapes arise. Some models emphasize the role of binary companions, whose gravitational pull can funnel outflows into jets or disks. Others focus on magnetic fields or on changes in the stellar wind over time. The fine-scale filaments and arcs visible in the Webb image may preserve a record of these competing influences, encoded in the directions and thicknesses of individual features. Detailed modeling of the nebula’s three-dimensional structure, constrained by the new data, could help discriminate among scenarios.
PMR 1 also illustrates how different observatories, separated by decades, can build a coherent narrative of stellar evolution. Spitzer provided the first clear infrared detection and the nickname that captured the public imagination. Webb, with its far greater sensitivity and resolution, now fills in the missing details. Future facilities may extend this story into other wavelengths, such as high-energy X-rays that trace the hottest shocked gas, or radio observations that map the coldest molecular remnants lingering at the nebula’s outskirts.
A Window into Stellar Futures
For all its eerie beauty, the Exposed Cranium Nebula is also a preview of the distant future of stars like our Sun. In roughly five billion years, the Sun is expected to exhaust its core hydrogen, expand into a red giant, and eventually shed its outer layers in a similar fashion. By examining objects such as PMR 1, astronomers are effectively reading the end chapters of a stellar life story that has only reached its middle pages in our own solar system.
The new Webb image underscores how much more there is to learn about those final chapters. Subtle asymmetries in the nebular shell hint at processes that may be invisible in earlier phases, from unseen companions to episodic mass loss. The clumpy dust traced by MIRI suggests that even as a star is dying, it is actively seeding its surroundings with the raw material for future generations of planets. And the sharp boundary between ionized and molecular gas offers a natural laboratory for studying how intense radiation reshapes interstellar clouds.
As one of the flagship missions of NASA, the James Webb Space Telescope is designed to tackle questions ranging from the first galaxies to nearby exoplanets. Yet its portrait of PMR 1 demonstrates that even relatively modest, well-known targets can yield transformative insights when viewed with new eyes. The Exposed Cranium Nebula, once a fuzzy curiosity in archival images, has become a benchmark object for understanding how Sun-like stars die, how they return material to the galaxy, and how that recycled matter sets the stage for whatever comes next.
For the teams at institutions such as the Jet Propulsion Laboratory and partner observatories worldwide, PMR 1 is likely to remain a touchstone as Webb continues its survey of stellar remnants. Each new planetary nebula imaged in comparable detail will add another data point to a growing comparative atlas of stellar endings. Together, these observations promise not only to refine models of individual objects, but also to illuminate the broader life cycle of matter in the Milky Way, from the quiet glow of dying stars to the birth of new systems that may one day host planets of their own.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
