In a groundbreaking study, a team of astronomers has identified four new X-ray supernova remnants (SNRs) in the flocculent spiral galaxy NGC 7793, located approximately 12 million light-years from Earth. This surprising finding Maria Kopsacheili, Institute of Space Sciences (ICE-CSIC), Barcelona, Spain This remarkable discovery was led by a major. Her pioneering observational techniques were used to study and understand the galaxy’s X-ray emissions.
The research team employed NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton satellite to conduct a detailed analysis of NGC 7793. On June 10, 2025, they released their results on the arXiv pre-print server. Their ongoing research has revealed several X-ray sources, among them five that coincide with all known optical supernova remnants (SNRs). In this study, an international group of scientists have greatly increased their understanding of the clouds that are the solidified remnants of exploded stars.
Observational Techniques and Findings
It took the astronomers a massive collective effort to investigate. To create their striking image, they combined multiple wavelengths together Hα + [N II] shown in red, soft X-rays in green (0.5 – 1.2 keV), and medium and hard X-rays shown in blue (1.2 – 7.0 keV). Such a wide-ranging approach meant they could study everything in archival data collected over 19 years, which resulted in just under 30 hours of observations (229.9 kiloseconds).
Within NGC 7793, the team found not one, but dozens, of X-ray sources during their examination. Five sources—X11, X13, X15, X25, and X38—were particularly fruitful, as these directly overlapped with optical SNRs. In all cases they showed offsets less than 1.3 arcseconds. In particular, the source X15 had been previously catalogued as an X-ray SNR. Beyond that, the detection of the new sources represents a major step forward in the study of supernova remnants in this nearby galaxy.
Characteristics of New Supernova Remnants
Among the newly discovered X-ray supernova remnants, X11, X13, X25, and X38 have X-ray luminosities of 0.88 to 5.49 undecillion erg/s. They are especially well known for their peculiar soft X-ray emission. This kind of emission means that the surroundings are much cooler than other astronomical objects.
Surprisingly to the researchers, none of these new SNRs exhibited any of the notable short- or long-term variability seen in the emissions from Galactic SNRs. This latest finding indicates the remnants now exist in an intermediate or stable stage of their development. In addition to these discoveries, two other candidate SNRs—X23 and X42—were found. Though these sources show soft, non-variable X-ray emission, they have never been seen in the optical.
Implications for Future Research
The confirmation of four new X-ray supernova remnants in NGC 7793 adds highly valuable data to the field of astrophysics. This unexpected result has broader implications, increasing our understanding of stellar evolution and supernovae process. With four of these remnants, it was Chandra’s high spatial resolution that was key to accurately identifying these remnants.
This study is an important addition to our incomplete catalog of supernova remnants. Additionally, it lays the groundwork for more in-depth studies of stellar evolution and supernova explosion mechanics. NGC 7793 will continue to be analyzed and we can expect many more discoveries relating to SNRs. These findings will help us piece together their role as galactic building blocks.