NASA astronomers have used the Nuclear Spectroscopic Telescope Array (NuSTAR) to spot a glow of high-energy X-rays emanating from the heart of the Milky Way galaxy. The origin of the mysterious glow is unknown, with scientists speculating that it may be caused by dead stars as they draw material from their stellar partners.
The new observations would not have been possible without the NuSTAR array, which is the first orbiting telescope designed to collect light in the high energy X-ray region of the electromagnetic spectrum. The glow in question was emitted from a region some 40 light-years across, located around the supermassive black hole at the core of our home galaxy.
The origin of the unexpected haze of high-energy X-rays observed in the region is puzzling astronomers, with numerous explanations being put forward.
When stars that are part of a binary system reach the end of their life, they can siphon matter from their stellar partner. The particulars of the process differ depending on the specific nature of the stars, but the result is often the eruption of X-rays. For this reason, many scientists believe that the newly observed region of high-energy X-ray activity is due to a large population of dying binary stars.
One theory singles out pulsars – the fast-spinning remnants of a supernova explosion – as the type of star causing the emissions, with the extreme rotation causing the intense beams of radiation. Other scientists suggest that it could be white dwarfs causing the readings, with the dense nature of the elderly stars affording them stronger gravity, which can produce higher energy X-rays than normal.
An alternative theory suggests that the observed X-rays might not be the product of dying stars at all, but might instead be a haze of charged particles known as cosmic rays originating from the supermassive black hole. It's thought that as these cosmic rays interact with the dense clouds of gas, they may emit the observed X-rays.
"This new result just reminds us that the galactic center is a bizarre place," said study co-author Chuck Hailey of Columbia University. "In the same way people behave differently walking on the street instead of jammed on a crowded rush hour subway, stellar objects exhibit weird behavior when crammed in close quarters near the supermassive black hole."
NASA plans to conduct further observations of the region in order to solve the mystery. In the meantime, the scientific community will likely continue its excited speculation, coming up with new models that explain the unusual find.