Astronomers discover new class of Hypersoft X-ray Sources

Astronomers have identified a new class of cosmic objects known as Hypersoft X-ray Sources (HSSs) after analyzing archival data from NASA’s Chandra X-ray Observatory collected between 1999 and 2017.

Researchers from the University of Alabama and the Center for Astrophysics | Harvard & Smithsonian discovered these highly luminous emitters by examining the lowest energy levels of the X-ray spectrum. Traditionally, astronomers have ignored these “soft” X-rays because detectors are often not calibrated for them. However, these objects emit a specific ratio of eight soft photons for every one hard photon, with emissions concentrated between 150 and 300 eV.

The discovery may help solve long-standing astronomical mysteries. These sources could represent precursors to certain types of supernovas or exotic configurations, such as triple-star systems containing two collapsed black holes. Because extreme ultraviolet light is often blocked by interstellar hydrogen and helium, these soft X-ray emissions provide a vital way for scientists to observe objects that were previously difficult to detect.