Sagittarius C may host a young supernova remnant

The centre of the Milky Way has diffuse X-ray emission whose explanation may involve hot plasma, unresolved point sources and different energetic processes. Sagittarius C, abbreviated Sgr C, lies within this environment and contains both star-forming and nonthermal activity. Its X-ray properties had received relatively little attention. A study published on 16 April 2026 in The Astrophysical Journal revisits the region using archival data from the Chandra and XMM-Newton observatories. It describes two components of diffuse emission and proposes a possible explanation for some of the hot gas.

A complex region at the Galactic centre

Sgr C lies on the western edge of the central molecular zone, or CMZ, a region of the Milky Way that hosts a mixture of star-forming and nonthermal activity. That combination means the observed emission should not be attributed from the outset to a single source or process. The study aims to better characterize the X-ray emission in this environment and examine how it relates to structures observed at other wavelengths.

The research also builds on earlier observations. The team using the Suzaku observatory was the first to propose a supernova remnant in Sgr C. However, Suzaku’s limited angular resolution and the offset between the peak of diffuse X-ray emission and the H II region meant that an association between the plasma and that region could not be firmly established. The new analysis uses archival observations from Chandra and XMM-Newton to examine the morphology and spectral properties in greater detail.

Two X-ray components

By combining data from the two observatories, the authors distinguish two components of diffuse emission. One coincides with the H II region and the radio-emission peak. The other is a brighter diffuse feature to the southwest. This distinction matters because it allows areas that may previously have been blended in the observed image to be described separately; on its own, it does not determine what produced either component.

Spatially resolved spectroscopy finds a soft plasma component in both areas, with a temperature of kT ≤ 1 keV. The H II region also contains a harder thermal component of about 8 keV. In addition, the measured metal abundances are consistent with the elevated metallicity expected in the CMZ. These findings describe the properties of the X-ray-emitting gas; by themselves, they do not identify its origin or the mechanism that heated it.

The clue of an expanding shell

The proposed interpretation links the diffuse X-ray emission to an expanding shell seen in a [C II] emission map. According to the authors, this association suggests that the hot gas may come from a young supernova remnant embedded in the H II region. The wording is conditional: the paper presents a possible relationship between observed structures, not a definitive identification of the remnant.

Under this interpretation, the inferred shock velocity is about 800 km s⁻¹, and the estimated remnant age is at least 1.7 × 10³ years. The authors consider both estimates consistent with a core-collapse supernova remnant at the Galactic centre. In this type of supernova, the core of a high-mass star collapses at the end of its life. In Sgr C, however, the velocity and age are inferences associated with the proposed interpretation of the emission and shell.

What the data show—and what remains open

The central observational result is that Sgr C’s diffuse emission can be separated into two components, along with a spectral characterization of the plasma in each area. The possible link to the [C II] shell offers an explanation for the hot gas, but the paper itself says that it may originate in a young remnant. That qualification matters: “may” is not confirmation, and the estimates of velocity and age must be understood within the same interpretation.

The earlier observations also show why the association calls for caution: Suzaku’s data could not firmly establish that the plasma was linked to the H II region. The new work provides more detail on the emission and a hypothesis connecting the X-rays with the [C II] shell, but that does not make the connection certain. Its conclusion is that Sgr C is a potential site of a supernova remnant. The research article presents the analysis and its results.

Why the distinction matters

Remnants are the structures studied after a stellar explosion; in this case, the question is not only whether hot gas is present, but whether the different signals in Sgr C are related in the way proposed. Distinguishing observation from interpretation avoids presenting as confirmed fact what the data support only as a hypothesis. The two X-ray components, the measured temperatures and the [C II] shell are elements of the analysis; the link between them and a young remnant remains an explanation the authors consider possible.

The study therefore provides a more detailed characterization of Sagittarius C’s X-rays and a clue to their possible origin. The most faithful reading is that the data support the possibility of a young remnant, while the association between the hot gas and the observed shell remains an interpretation rather than a definitive identification.