Credit: Credit: X-ray: NASA/CXC/Univ. of Alabama/M. Muhibullah et al.; Optical: NASA/ESA/STScI; Image Processing: NASA/CXC/SAO/N. Wolk
Brand New Soft Things
Who knows what lurks in the depths of NASA's X-ray data archives? Take the Chandra X-ray Observatory, for example. Chandra has targetted thousands of individual X-ray sources of interest to X-ray astrophysicists. But with each observation, hundreds of additional sources photobomb Chandra's field of view. Many of these are stars in the Milky Way or other previously identifiable objects. But other unusual objects may be waiting there for discovery by painstaking, detailed analysis. A recent study of X-ray color images of external galaxies observed by Chandra for more than 20 years since Chandra's launch revealed a weird class of point-like objects in the hinterlands of some of the galaxies. These new objects emit most of their radiation at low X-ray energies, and are very luminous, radiating in the low-energy X-ray band more than 100,000 times the luminosity that the Sun radiates over all energies. Because these objects radiate in the low energy, or "soft", X-ray band, astronomers now refer to them "hyper-soft" sources. The image above shows a composite of a Chandra X-ray image and an optical image of the face-on galaxy M101; the hypersoft sources are shown by orange circles. As of now, it's not certain what these objects may be. Suggestions include white dwarfs accreting from a companion star, white dwarfs that have undergone a nova eruption, or perhaps some type of mysterious black-hole system. What else might be lurking, waiting only for discovery by some enterprising sleuth? Search for yourself.
Published: September 21, 2026
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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 28-Sep-2026 11:58:29 EDT