With help from NASA’s Nuclear Spectroscopic Telescope Array (otherwise known as NuSTAR), astronomers have ‘heard’ what they believe to be the death cries of stars that are being systematically destroyed by their companions—their screeching comes in the form of strange high-energy x-ray emission, seen emanating from our galaxy’s center.
Found approximately 20,000 – 26,000 light-years from Earth, this region is the hub of our galaxy, filled with a wide-variety of cosmological objects, all densely packed within a small area of spacetime. These objects include populations of old and new stars, a large molecular cloud called Sagittarius B2 (Sgr B2), and a heavy-weight black hole known as Sagittarius A*.
The black hole specifically has been the source of a lot of interest in the scientific community, but up until NuSTAR was dispatched in 2012, we were unable to resolve this region with the same level of clarity.
In addition to the normal activity, the latest images, which zero in on a section of sky just 40 light-years across, picked up strange signatures coming from an unknown source.
“Almost anything that can emit X-rays is in the galactic center,” notes the study’s lead author, Kerstin Perez (from Columbia University in New York). “The area is crowded with low-energy X-ray sources, but their emission is very faint when you examine it at the energies that NuSTAR observes, so the new signal stands out.”
To explain the anomaly, researchers have come up with several hypotheses. Of those four, only one doesn’t involve dense remnants of once-massive stars that went supernova. These objects include neutron stars and their counterparts, pulsars—or neutron stars that spin very fast, and shoot pulsating beams of high-energy radiation from their poles. If their poles are aligned toward Earth, they act as cosmic beacons of some sorts (hence the name).
Researchers suggest that, in the case of NuSTAR’s findings, pulsars may be at work, only they would need to have companions to siphon material from.
According to the team:
The problem, however, lies in the fact that we’ve never seen anything of the sorts prior to this. In fact, the observations appear to fly in the face of previous research conducted on our galaxy’s core.
“This new result just reminds us that the galactic center is a bizarre place,” remarks Chuck Hailey (also from Columbia University), one of the study’s co-authors. “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.”
“We can see a completely new component of the center of our galaxy with NuSTAR’s images,” But “we can’t definitively explain the X-ray signal yet—it’s a mystery. More work needs to be done,” Perez cautions.