NASA captures screams of zombie stars
High-energy X-rays at the centre of the Milky Way stump NASA astronomers.
NASA’s NuSTAR telescope may have captured the moans and groans of zombie-like stars feeding on their stellar companions. NuSTAR (Nuclear Spectroscopic Telescope Array) captures clear images of the centre of the Milky Way in high-energy X-rays.
New images sent back show a haze of these rays dominating the chaotic region in the middle of the Galaxy that surrounds a supermassive black hole called Sagittarius A*.
"We can see a completely new component of the centre of our Galaxy with NuSTAR's images," says Kerstin Perez of Columbia University in New York, lead author of a report on the findings.
"We can't definitively explain the X-ray signal yet. It's a mystery."
Almost anything that can emit X-rays is in the galactic centre.
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."
Unlike the Sun, some stars exist as part of a binary or stellar pair, meaning two stars that orbit about their common centre of mass.
Sometimes when these types of star collapse and die, they begin acquiring matter from their other half.
This process can sometimes result in an eruption of X-rays.
NASA says another explanation could be a type of stellar ‘zombie’ called a pulsar, which are the collapsed remains of stars that have exploded as a supernova.
These remnants emit radiation as they spin furiously through space.
Other theories include white dwarfs, which are collapsed stars not big enough to become a supernova.
As these stars get denser, their gravitational pull increases and they begin producing higher energy X-rays.
Or, it could be the result of small black holes feeding off their companion stars, which would cause an emission of X-rays.
Alternatively, the high energy could be a haze of cosmic rays; charged particles that travel through space at nearly lightspeed.
Ultimately, astronomers are as yet unsure what is causing the high-energy, X-ray glow.
"This new result just reminds us that the galactic centre is a bizarre place," says 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 behaviour when crammed in close quarters near the supermassive black hole."
"Every time that we build small telescopes like NuSTAR, which improve our view of the cosmos in a particular wavelength band, we can expect surprises like this," adds Paul Hertz, astrophysics division director at NASA Headquarters.
Iain Todd is BBC Sky at Night Magazine's Staff Writer. He fell in love with the night sky when he caught his first glimpse of Orion, aged 10.