Scientists Found Strange Objects in Space: 84 Hypersoft X-ray Sources
Astronomers using archived data from NASA's Chandra X-ray Observatory have identified 84 hypersoft X-ray sources in six galaxies, including Andromeda and Pinwheel. The objects emit unusually low-energy X-rays and intense ultraviolet light, and may help explain Type Ia supernovae.
Scientists found strange objects in six galaxies after combing through archived data from NASA's Chandra X-ray Observatory, identifying 84 sources that astronomers describe as a new class of cosmic object. The team calls them hypersoft X-ray sources.
The objects appear in data Chandra collected between 1999 and 2017. That suggests more of them may still be sitting in the archive.
What makes them unusual
Hypersoft X-ray sources emit unusually low-energy X-rays and intense levels of ultraviolet radiation. They turned up in six galaxies, including the Andromeda and Pinwheel galaxies.
The team found them by comparing images taken at different X-ray energies. The new objects showed up only in the images taken at the lowest energies.
"We’ve never encountered a group of objects that act like this," said lead researcher Mustafa Muhibullah of the University of Alabama.
What they could be
Researchers believe the sources may be binary systems. In such a system, a compact object, possibly a white dwarf, neutron star or black hole, pulls material from a companion star. The falling material heats up and gives off radiation.
That behavior could bear on two long-standing puzzles. The first concerns Type Ia supernovae, which astronomers use to measure the expansion of the Universe. The scenarios that trigger these explosions remain uncertain, and the new sources could be a candidate.
"If we could find a way to spot these Type Ia supernova explosions before they go off, that would be really important," said co-author Jimmy Irwin.
The second puzzle is the source of the radiation that strips electrons from diffuse gas in and around galaxies. That process helps shape star formation. The ultraviolet output of the new objects may supply part of the missing radiation.
Why they stayed hidden
Low-energy X-rays are hard to detect. Ultraviolet radiation is readily absorbed by hydrogen and helium gas between the stars.
"By combing through the Chandra archive, we were able to eliminate what used to be a blind spot for telescopes," said co-author Rosanne Di Stefano.
Dian Triani at Harvard led work last year showing that many galaxies have signs of excited gas even without a bright active galactic nucleus to power it. Objects like these appear to provide enough high-energy radiation to affect their surroundings.
The team now hopes to find more hypersoft X-ray sources and work out what powers them.
