Astronomers using NASA’s Chandra X-ray Observatory have identified a possible supernova remnant in the Sagittarius C region, about 26,000 light-years from Earth.
If confirmed, the candidate would rank among the closest ever detected to the Milky Way’s central supermassive black hole, and the team puts its age floor at about 1,700 years and its expansion speed at about two million miles per hour.
A Possible Stellar Aftermath in Sagittarius C
Using X-ray data from Chandra and ESA’s XMM-Newton, a team of astronomers has identified a “blob” of emission that may come from the remains of a massive star that self-destructed as a supernova, buried within a larger cloud of expanding gas. The candidate sits inside a bubble of ionized gas called an H II region, a bright radio source named Sagittarius C.
If confirmed, the find would rank among the closest supernova remnants ever discovered to the supermassive black hole at the central region of the Milky Way, according to NASA’s announcement of the Sagittarius C find. Sagittarius C sits in what the space agency described as “an exotic region crammed with massive stars, long threads of magnetic fields and dense clouds of gas orbiting rapidly around the Galactic Center.” Sagittarius C is a massive and active star-forming region on the western side of the central molecular zone, the paper notes, a setting where a young supernova remnant has been suspected since at least 2009. Supernova explosions of this kind provide iron, oxygen and silicon to the gas around them, material that goes into forming the next generation of stars and planets, the release notes, and supernova-forged iron has shown up in other settings, including in iron-60 supernova dust trapped in Antarctic ice.
If this is indeed a supernova remnant, then it is expanding at about two million miles per hour and is at least about 1,700 years old.
An Age, a Speed, and a Distance
The team set the candidate’s age and speed in a statement released with the new Chandra photo on June 11, 2026. Lead author Zhenlin Zhu of the University of California, Los Angeles, and his co-authors put the age floor at about 1,700 years and the expansion at about two million miles per hour, in the Astrophysical Journal paper on the Sagittarius C complex.
The candidate sits about 26,000 light-years from Earth, a distance that places it on the western edge of the central molecular zone, the paper notes. The paper describes Sagittarius C as a “massive and active star-forming region” and a “useful laboratory for testing theories of star formation in the relatively extreme environment of the CMZ.” For its analysis, the team adopts an average distance of 8.1 kiloparsecs to the galactic center, a scale used in recent work on the region.
The numbers carry their own scale. The paper infers a shock velocity of about 800 kilometers per second driving the candidate’s expansion, the kind of speed expected for a young core-collapse supernova remnant. An age of at least 1,700 years paired with that shock speed matches the profile of a massive star that ended in a self-destruction, the team writes. The candidate’s distance of about 26,000 light-years sits inside the 8.1 kiloparsec distance the paper adopts for the galactic center.
- Distance from Earth: about 26,000 light-years
- Age floor: at least about 1,700 years
- Expansion speed: about 2 million miles per hour
- Shock velocity: about 800 km/s
Why the Galactic Centre Matters
The Milky Way’s galactic center is one of the most studied and least understood places in astronomy. Some 26,000 light-years from Earth, it packs a supermassive black hole, Sagittarius A*, dense molecular clouds, and a population of massive young stars into a region only a few hundred light-years across. Sagittarius C is one of the major star-forming complexes in this inner zone.
Sagittarius C lies on the western edge of the central molecular zone, a region NASA described as “an exotic region crammed with massive stars, long threads of magnetic fields and dense clouds of gas orbiting rapidly around the Galactic Center.” The paper describes Sagittarius C as a “massive and active star-forming region” and a “useful laboratory for testing theories of star formation in the relatively extreme environment of the CMZ.” The diffuse X-ray emission in this kind of region is a complex mix of thermal and nonthermal components, the paper notes, so resolving a distinct supernova-remnant signal is a careful job. Sagittarius C is also the home of a bright radio source of the same name, an H II region of ionized hydrogen around a massive young star.
A supernova remnant inside Sagittarius C would put a fresh, well-localized point on the map of the zone, and a candidate of that kind, if confirmed, would rank among the closest supernova remnants known to the galactic center’s supermassive black hole. Whether the candidate holds up is the open question the paper leaves for follow-up work.
The new finding is part of a long-running effort to read the X-ray sky in the inner galaxy. Earlier Chandra and XMM-Newton work had traced a complex pattern of X-ray emission across the central molecular zone, much of it linked to past activity of the supermassive black hole at the center of the Milky Way. Sagittarius C stands out in that pattern as a place where stellar feedback, supernova explosions, and magnetic fields are all expected to be at work at once.
A Rival Reading From Stellar Winds
The candidate has a competing explanation. The X-ray emission could also come from a collection of massive stars in the region heating their surroundings, the NASA release notes, in a scenario that does not require a single stellar explosion.
The X-ray emission from the blob is more than ten times brighter than the X-ray emission of large, known stellar clusters with bright, massive stars, the authors write. That gap, they argue, makes a hot-gas origin from stellar winds unlikely. The paper adds that the candidate’s velocity and age match what a young core-collapse supernova would produce, not what a stellar wind or wind-blown bubble would normally reach. The team writes that the candidate’s numbers fit a young core-collapse blast from a massive star.
The team also looked for an elemental signature in the X-ray data, searching for signs of increased amounts of key elements such as iron, oxygen and silicon that a stellar explosion would have blasted into space. They did not see an enhancement, which they write could mean the stellar debris has already mixed with the surrounding gas.
| Attribute | Supernova remnant reading | Hot gas from massive stars reading |
|---|---|---|
| Source of the X-ray emission | A single massive star that self-destructed as a supernova | Hot gas from a collection of massive stars in the region |
| X-ray brightness vs. stellar clusters | More than ten times brighter than large, known stellar clusters | Comparable to the brightness of large, known stellar clusters |
| Prior shell evidence from SOFIA | Matches an expanding shell of gas that SOFIA mapped around the H II region | The shell’s expansion velocity is hard to explain by stellar feedback alone, per the team’s reading of prior work |
| Authors’ verdict | Favored; the data are ‘consistent with’ a young supernova remnant | Deemed unlikely |
How the Image Came Together
The new picture is a stack of instruments, not a single image. NASA released a composite that pulls together X-ray, radio, optical, and infrared data from five archival Chandra observations taken between July 2001 and August 2014, the Chandra photo page for the Sagittarius C find notes. The image credits X-ray data to NASA/CXC/UCLA/Z. Zhu et al. and ESA/XMM-Newton, optical to Pan-STARRS, radio to MeerKAT, and image processing to NASA/CXC/SAO/L. Frattare and P. Edmonds.
The X-ray signal itself comes from Chandra and XMM-Newton, with the Chandra exposure totaling 197 kiloseconds of clean data across the five observations. The X-ray view is overlaid on a radio image from the MeerKAT telescope in South Africa and an optical background from the Pan-STARRS telescopes in Hawaii. A second version of the image adds infrared data from NASA’s James Webb Space Telescope, with the H II region glowing in light blue and the candidate’s X-ray signature in a darker blue on the right side of the frame. The plane of the Milky Way runs left to right across the image, and the central supermassive black hole sits off to the left of the frame, the release notes.
- Chandra X-ray Observatory (NASA): five archival X-ray observations taken 2001 to 2014
- XMM-Newton (ESA): additional X-ray data for the same region
- MeerKAT (South Africa): radio image of the H II region and surrounding filaments
- Pan-STARRS (Hawaii): optical background showing the galactic plane
- James Webb Space Telescope (NASA/ESA/CSA): infrared view of the H II region
- SOFIA (NASA, now retired): prior infrared observations that mapped an expanding shell
A Long Look Back at Sagittarius C
Sagittarius C has been on astronomers’ maps for years. Suzaku observed the region in 2009 and was the first to propose a supernova remnant inside it, though the angular resolution of the time made the case inconclusive. The new paper builds on a 2021 Chandra survey of the central 2° by 4° field of the Galaxy and on JWST mapping of the complex in 2023.
Earlier infrared work from NASA’s now-retired SOFIA mission had already mapped an expanding shell of gas around Sagittarius C and raised the possibility of a recent supernova, giving the team the first hint that a stellar explosion had occurred in the same spot. The team’s new analysis uses archival Chandra and XMM-Newton observations to revisit the environment of the Sagittarius C H II region and resolves its diffuse X-ray emission into two components.
The open question is whether the X-ray blob is what the team says it is. NASA’s release uses “possible” and “candidate” throughout, and the paper itself frames the result as “consistent with” a young core-collapse supernova remnant, not a confirmed one. The candidate’s young age and its location inside the central molecular zone make it a natural target for the next round of X-ray work. Deeper spectroscopy of the candidate’s spectrum is the next step that would distinguish the two interpretations.
