NASA's Chandra spots 84 mystery 'hypersoft' X-ray objects across six galaxies
NASA's Chandra X-ray Observatory has revealed a new class of objects that emit unusually low-energy X-rays but intense ultraviolet light — and they could help solve two long-standing cosmic mysteries.
NASA’s Chandra X-ray Observatory has uncovered a new class of cosmic objects that behave like nothing astronomers have seen before, in a discovery that could help answer two long-standing questions about the universe.
The objects, dubbed “hypersoft X-ray sources”, give off unusually low-energy X-rays but intense levels of ultraviolet radiation, NASA said. The discovery is featured in a paper in Nature Astronomy led by Mustafa Muhibullah of the University of Alabama. “We’ve never encountered a group of objects that act like this,” he said.
The researchers found 84 of the sources across six galaxies by combing through the Chandra archive: two spirals — M31 (the Andromeda galaxy) and M101 (the Pinwheel galaxy) — and four ellipticals. They were spotted by finding objects that appeared in Chandra images taken at the lowest X-ray energies but vanished in higher-energy images.
The team believes the sources most likely involve a black hole, neutron star, or white dwarf pulling material from a companion star — binary systems that have been seen before, but never with such bright ultraviolet radiation and low-energy X-rays.
“These clandestine X-ray sources are actually among the most energetic objects in galaxies, and they could be solving two cosmic mysteries at once,” Muhibullah said. The first: identifying the stars that explode as Type Ia supernovae, which are critical for measuring the expansion of the universe and helped reveal that the expansion is accelerating. The second: what strips electrons from the gas between stars, which affects how quickly stars form and the life cycles of galaxies.
The objects went undetected until now partly because low-energy X-rays are very difficult for telescopes to pick up, and the ultraviolet radiation is readily absorbed by helium and hydrogen gas between the stars — a “nearly impenetrable barrier”, NASA said.
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