Webb Reveals the Inner Workings of the 'Exposed Cranium' Nebula, a Dying Star's Brain-Shaped Shroud
NASA's James Webb Space Telescope has captured the most detailed images yet of nebula PMR 1, nicknamed the Exposed Cranium, revealing a two-light-year-wide structure shaped by jets from a massive dying star roughly 5,000 light-years away in the constellation Vela.
Overview
NASA’s James Webb Space Telescope has turned its infrared instruments on one of the sky’s most visually striking objects: nebula PMR 1, a cloud of gas and dust roughly 5,000 light-years away in the constellation Vela whose uncanny resemblance to a brain inside a transparent skull has earned it the nickname the “Exposed Cranium.” The new observations, released by the Space Telescope Science Institute on February 25, 2026, represent the sharpest view yet of the structure, which spans approximately two light-years in diameter and surrounds a massive star in the final stages of its life.
What Webb Found
Webb observed PMR 1 using both its Near-Infrared Camera (NIRCam) and its Mid-Infrared Instrument (MIRI), capturing the nebula across wavelengths ranging from 1.5 to 18.0 microns. The near-infrared images, taken at 1.5, 1.87, 4.44, and 4.70 microns, reveal the nebula’s early hydrogen ejecta and complex, dusty internal structure. The mid-infrared images, at 10.0, 11.3, 12.8, and 18.0 microns, highlight the heated dusty interior that gives the object its brain-like texture.
The nebula displays two distinct evolutionary layers. An outer shell, composed primarily of hydrogen, represents material that was expelled first as the star began shedding its atmosphere. Inside that shell sits a more structured inner cloud containing a mix of different gases and dust, visible in far greater detail than in any previous observation.
A distinctive dark lane runs vertically through the center of the nebula, dividing it into what appear to be left and right hemispheres and reinforcing its brain-like appearance. Webb’s high resolution suggests that this dark lane is connected to powerful jets shooting outward from the central star in opposite directions. Evidence of this outflow is especially visible in MIRI’s mid-infrared data near the top of the nebula, where gas appears to be pushed outward from the inner region.
From Spitzer to Webb
PMR 1 was first detected in infrared light more than a decade ago by NASA’s now-retired Spitzer Space Telescope. While Spitzer identified the basic structure, its instruments lacked the resolution to reveal fine details within the nebula. Webb’s instruments provide a dramatically sharper view, resolving the multiple ejection layers and the jet-driven morphology that Spitzer could only hint at. Data from ESA’s Gaia observatory had also shown that the nebula suffers from severe reddening, meaning dust between Earth and PMR 1 absorbs and scatters much of its visible light, making infrared observation essential.
An Uncertain Fate
The central star of PMR 1 is several times more massive than the Sun, but its precise mass remains undetermined. That measurement matters because it will determine the star’s ultimate fate. If sufficiently massive, it will exhaust its nuclear fuel and explode as a supernova, scattering heavy elements into the surrounding interstellar medium. If it falls below that threshold, it will continue to shed its outer layers more gradually until only a dense, hot core remains, becoming a white dwarf that will cool over cosmic timescales.
In either scenario, the material the star is currently expelling will enrich the surrounding region with the chemical elements needed for future generations of stars and planets. The Exposed Cranium nebula thus offers a snapshot of one of the fundamental processes driving chemical evolution in the Milky Way, now seen in unprecedented infrared detail.