Discovery of hypersoft X-ray sources in galaxies

Astronomers using data from NASA’s Chandra X-ray Observatory have identified a new class of celestial objects, described as “hypersoft X-ray sources” or “ultrasoft X-ray sources.” Researchers located 84 of these sources across six different galaxies, including the spiral galaxies M31 and M101, as well as four elliptical galaxies.

These objects are distinguished by emitting unusually low-energy X-rays alongside intense ultraviolet radiation. This specific signature makes them difficult to detect because the high-energy ultraviolet radiation is often absorbed by neutral hydrogen and helium in the interstellar medium. The discovery was made by analyzing existing public data from the Chandra archive rather than through a new observation campaign.

While the exact nature of these sources is still being studied, scientists hypothesize they involve binary star systems where a compact object—such as a black hole, neutron star, or white dwarf—is accreting material from a companion star. The phenomenon appears to occur in diverse environments, ranging from active star-forming regions to areas dominated by older stars.