NASA observatory detects mysterious cosmic explosion
Washington: A mysterious flash of X-rays probably resulting from a “completely new type of cataclysmic event” in space has been discovered by NASA’s Chandra X-ray Observatory, a study says.
While the scientists believe the flash of X-rays, which stemmed from a faint, small galaxy about 10.7 billion light years from Earth, likely comes from some sort of destructive event, they are not sure what caused it.
“We may have observed a completely new type of cataclysmic event,” said study co-author Kevin Schawinski, of ETH Zurich (Swiss Federal Institute of Technology in Zurich) in Switzerland.
“Whatever it is, a lot more observations are needed to work out what we’re seeing,” Schawinski added.
The X-ray source, located in a region of the sky known as the Chandra Deep Field-South (CDF-S), has remarkable properties.
Prior to October 2014, this source was not detected in X-rays, but then it erupted and became at least a factor of 1,000 brighter in a few hours.
After about a day, the source had faded completely below the sensitivity of Chandra.
Thousands of hours of legacy data from the Hubble and Spitzer Space Telescopes helped determine that the event likely came from a faint, small galaxy about 10.7 billion light years from Earth.
For a few minutes, the X-ray source produced a thousand times more energy than all the stars in this galaxy, said the study published online in the journal Monthly Notices of the Royal Astronomical Society.
“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.
“It’s like we have a jigsaw puzzle but we don’t have all of the pieces,” Bauer added.
There are three main possibilities to explain the X-ray source, according to scientists.
Two of them invoke gamma-ray burst (GRB) events which 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, 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,” study co-author Ezequiel Treister, also of the Pontifical Catholic University, noted.