Mysterious X-ray flash in deep space has astronomers baffled
A mysterious flash of X-rays has been spotted by Nasa's Chandra X-ray Observatory in deep space, and astronomers are at a loss to explain it.
The X-ray source, located in a region of the sky known as the Chandra Deep Field-South (CDF-S), was unremarkable before October 2014 - but then it erupted and became at least 1000 times brighter in a few hours. After about a day, the source had faded to the point that it couldn't be detected by Chandra.
"Ever since discovering this source, we've been struggling to understand its origin," said Franz Bauer of the Pontifical Catholic University of Chile in Santiago, Chile. "It's like we have a jigsaw puzzle but we don't have all of the pieces."
Two of the three main possibilities to explain the X-ray source invoke gamma-ray burst (GRB) events. GRBs are jetted explosions triggered either by the collapse of a massive star or by the merger of a neutron star with another neutron star or a black hole. If the jet is pointing towards the Earth, a burst of gamma rays is detected. As the jet expands, it loses energy and produces weaker, more isotropic radiation at X-ray and other wavelengths.
Possible explanations for the CDF-S X-ray source, according to the researchers, are a GRB that is not pointed toward Earth, or a GRB that lies beyond the small galaxy. A third possibility is that a medium-sized black hole shredded a white dwarf star.
"None of these ideas fits the data perfectly," said Ezequiel Treister, also of the Pontifical Catholic University, "but then again, we've rarely if ever seen any of the proposed possibilities in actual data, so we don't understand them well at all."
No similar events have been found by Chandra in other parts of the sky.