NASA's Chandra Telescope Discovers 84 Mysterious Supersoft X-ray Sources

NASA's Chandra X-ray Observatory recently announced that researchers using the observatory's publicly available observation data discovered 84 mysterious celestial objects known as “supersoft X-ray sources” in 6 galaxies. The related research was published in Nature·Astronomy.

Image credit: X-ray: NASA

These objects emit X-rays with unusually low energy and may be accompanied by strong high-energy ultraviolet radiation. The research team stated that the behavior of these objects is clearly different from previously observed known celestial bodies and may provide new clues for explaining the origin of Type Ia supernovae and the electron-stripping mechanism in the intergalactic medium.

The 6 galaxies covered by this search include two spiral galaxies, M31 (the Andromeda Galaxy) and M101 (the Pinwheel Galaxy), as well as 4 elliptical galaxies. The researchers found that these supersoft X-ray sources exist both in regions of active star formation and in regions populated by old stars. By comparing Chandra's low-energy and high-energy X-ray images, the research team identified radiation sources visible in the low-energy images but absent in the high-energy images, thereby determining that they release far more low-energy X-rays than high-energy X-rays.

At present, the type of celestial objects producing this radiation has not yet been determined. The researchers believe that the more likely scenario is that black holes, neutron stars, or white dwarfs are accreting matter from companion stars, with the matter being heated and producing X-rays before falling onto the compact object. Similar binary star systems have been observed before, but cases simultaneously exhibiting such bright ultraviolet radiation and low-energy X-rays have not been found.

The research team pointed out that if some supersoft X-ray sources are related to white dwarf systems accreting matter, they may be connected to the formation of Type Ia supernovae. Type Ia supernovae are often used to measure cosmic expansion, but their pre-explosion progenitor systems have long been difficult to directly confirm. If the relevant systems can be identified before the explosion, it would help understand the source of material that triggers the supernova explosion.

In addition, the strong ultraviolet radiation released by supersoft X-ray sources may also participate in stripping electrons from gas atoms within galaxies. This process affects the rate of star formation and further influences galaxy evolution. The researchers stated that low-energy X-rays themselves are relatively difficult for telescopes to detect, and high-energy ultraviolet radiation is easily absorbed by hydrogen and helium in interstellar space, which may be an important reason why such celestial objects had long gone undiscovered. By re-examining the Chandra telescope's archival data, the researchers were able to identify this new class of cosmic objects with special radiation characteristics.