Forty million years ago, a massive star in a nearby galaxy tore itself apart in a violent explosion, and astronomers have now identified the exact star responsible. Using pre-explosion images from NASA’s James Webb Space Telescope, a research team led by Charlie Kilpatrick of Northwestern University matched a single red supergiant to the site of supernova SN 2025pht in galaxy NGC 1637, making it the first time JWST has directly detected a supernova progenitor star. The discovery reshapes how scientists understand the final stages of stellar life, particularly the role dust plays in obscuring dying stars from view.
The work draws on a growing ecosystem of space-based observatories and data archives coordinated through NASA’s broader science programs, which knit together optical, infrared, and time-domain surveys. In this case, the combination of ground-based discovery, Hubble imaging, and JWST’s infrared vision turned a single supernova into a detailed case study of stellar death. By tying a specific explosion to a specific star, astronomers can now test long-standing theories about how red supergiants live and die against a concrete, data-rich example.
A Red Supergiant Caught Before the Blast
The light from SN 2025pht first reached Earth on June 29, 2025, when the All-Sky Automated Survey for Supernovae (ASAS-SN) flagged a new transient in NGC 1637. But the real breakthrough came from looking backward in time. Pre-explosion images captured by both the Hubble Space Telescope and JWST in 2024 revealed a single red supergiant at the supernova’s position, with no competing sources nearby. That precise alignment, coupled with the star’s disappearance in post-explosion imaging, gave the team high confidence that they had found the progenitor that ultimately detonated as SN 2025pht.
Spectral analysis classified SN 2025pht as a Type II supernova, defined by broad hydrogen lines in its spectrum, according to the team’s detailed preprint on the event. A more focused follow-up analysis refined the classification to Type II-Plateau, a subtype where the supernova’s brightness remains nearly constant for several weeks before fading as the ejecta cools and recombines. NGC 1637 sits roughly 12 million parsecs from Earth, though an independent modeling effort estimates a distance of 10.73 plus or minus 1.76 Mpc, a discrepancy that highlights the intrinsic uncertainties in extragalactic distance scales rather than any disagreement about the progenitor’s identity.
Dust That Hid a Dying Star
What sets this discovery apart from previous progenitor detections is the star’s extreme redness. The progenitor appeared far redder than typical red supergiants, and the reason turned out to be a vast shell of carbon-rich dust surrounding the star. That dusty cocoon acted like a selective filter, absorbing shorter, bluer wavelengths and allowing only the longest infrared light to escape. Without JWST’s mid-infrared sensitivity, the progenitor would have been nearly invisible, and the connection between the star and the supernova might never have been made.
Pre-explosion detections from HST and JWST span wavelengths from 1.3 to 8.7 micrometers, giving astronomers enough coverage to construct a detailed spectral energy distribution and model the dust envelope’s properties. Carbon-rich dust is not unusual around evolved stars, but the thickness of this shell suggests an episode of intense mass loss in the star’s final centuries or decades. One possibility, flagged in a separate variability-focused analysis, is that the progenitor exhibited brightness changes with a roughly 660-day period, hinting at strong pulsations or even subtle interactions with a companion star that could have accelerated the shedding of material and built up the dense circumstellar environment.
Why JWST Changed the Game for Progenitor Hunting
Before JWST, astronomers relied almost entirely on Hubble to hunt for progenitor stars in archival images. Hubble operates mainly in optical and near-infrared light, which means heavily dust-enshrouded stars like the progenitor of SN 2025pht were effectively hidden from view. JWST’s mid-infrared instruments changed that equation. By imaging NGC 1637 in 2024 as part of its regular observing programs, the telescope captured the progenitor at wavelengths Hubble could not reach, and the associated release from the science team confirmed that the star was embedded in a thick shell of carbon-rich dust that only mid-infrared imaging could penetrate.
This matters because it implies that an entire population of supernova progenitors may have been missed by earlier, optical-only surveys. If dust-enshrouded red supergiants are common precursors to Type II explosions, then the historical record of progenitor detections is incomplete and biased toward cleaner, less obscured environments. The SN 2025pht case is a single example, but it demonstrates the technical capability to find more such stars as JWST continues to monitor nearby galaxies. Each new supernova occurring in a field that JWST has already imaged becomes a natural experiment: astronomers can return to the archive, search for a progenitor in the infrared, and compare its properties to what the explosion ultimately produced.
What Dust Tells Us About Stellar Death
The carbon-rich dust shell around SN 2025pht’s progenitor is not just an observational nuisance. It is a physical record of what the star was doing in the run-up to its destruction. Red supergiants lose mass through slow, dense stellar winds, and the composition and geometry of the resulting dust encode information about the star’s internal chemistry and surface conditions. In this case, the carbon-rich signature suggests that the star had dredged up processed material from deep within its interior, indicating that nuclear burning had advanced to late stages and that convection was mixing those products into the outer layers where they could condense into dust.
The potential 660-day variability period identified in the separate analysis adds another dimension. Long-period variability in red supergiants is often associated with large-scale radial pulsations that can enhance mass loss by periodically lifting material off the star’s surface. If further observations confirm this periodicity, it could directly link the observed dust production to the star’s internal dynamics in its final years. That kind of connection (between pre-explosion behavior, circumstellar environment, and the resulting supernova) is exactly what theorists need to refine models of which stars explode, how much mass they lose beforehand, and how those conditions shape the brightness and evolution of the eventual blast.
A New Standard for Supernova Science
The identification of SN 2025pht’s progenitor sets a new benchmark for what astronomers can learn from a single stellar death. By combining time-domain surveys, Hubble imaging, and JWST’s infrared power, the research team has produced a multi-wavelength portrait that stretches from the star’s quiet, dust-shrouded phase through its violent demise and into the expanding debris field that now marks its former location. This kind of end-to-end coverage is increasingly reflected across NASA’s science news updates, where supernova discoveries are framed not just as isolated flashes but as parts of longer, traceable life cycles.
Looking ahead, astronomers expect that JWST will transform supernova progenitor studies from rare, opportunistic finds into a more systematic enterprise. As more nearby galaxies are observed in the infrared, the odds increase that future supernovae will occur in regions with deep pre-explosion coverage. Those events will feed into a growing catalog of progenitors with measured masses, luminosities, dust environments, and variability patterns. That catalog, in turn, will inform theoretical models and will likely be highlighted in recently published research roundups, shared through digital video explainers, and discussed on NASA’s podcast and audio channels as scientists work to weave individual cases like SN 2025pht into a coherent story of how the most massive stars in the universe live, die, and seed space with the elements for new generations of stars and planets.
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*This article was researched with the help of AI, with human editors creating the final content.
