Astronomers using NASA’s Chandra X-ray Observatory have identified a class of objects that emit unusually soft, low-energy X-rays while likely producing intense ultraviolet radiation. The 2026 study found 84 of these “hypersoft X-ray sources” across six galaxies, including the face-on spiral galaxy M101.
Quick facts
- The survey identified 84 hypersoft X-ray sources in six galaxies.
- The sources appear at Chandra’s lowest X-ray energies and fade at higher energies.
- Researchers consider systems containing white dwarfs, neutron stars or black holes accreting from companion stars among the leading explanations.
- M101 is about 21 million light-years from Earth.
Why this matters
The sources are interesting because they may connect to two difficult problems. Some could be related to binary systems that eventually produce Type Ia supernovae, which are important cosmic distance markers. Their ultraviolet output may also contribute to ionizing gas in galaxies. Because low-energy X-rays and energetic ultraviolet light are easily absorbed, such sources can be hard to find even when they are intrinsically powerful.
How to read this result
For unusual X-ray sources, their energy distribution and behavior across other wavelengths are essential for identifying the underlying compact object. The survey identified 84 hypersoft X-ray sources in six galaxies. The sources appear at Chandra’s lowest X-ray energies and fade at higher energies. Together, those measurements give the visual feature a testable physical meaning and help researchers compare it with earlier observations and models.
What comes next
Follow-up work will test which kinds of compact objects are present and whether all hypersoft sources belong to one physical class. Longer observations and multiwavelength data will be needed to separate white-dwarf systems from neutron-star or black-hole binaries.