Is this Mystery Science Theater?
Zombie stars? Howling? Sounds like a new horror film star, not an observation from NASA's NuSTAR. The Nuclear Spectroscopic Telescope Array has spotted a mysterious glow of high-energy X-rays that, according to scientists, could be the "howls" of dead stars as they feed on stellar companions.
(Cue Vincent Price!)
"We can see a completely new component of the center of our galaxy with NuSTAR's images," said lead author Kerstin Perez of Columbia University, according to a press release. "We can't definitively explain the X-ray signal yet - it's a mystery. More work needs to be done."
The center of our Milky Way galaxy is bustling with young and old stars, smaller black holes and other varieties of stellar corpses - all swarming around a supermassive black hole called Sagittarius A*.
NuSTAR, launched into space in 2012, is the first telescope capable of capturing crisp images of this frenzied region in high-energy X-rays. The new images show a region around the supermassive black hole about 40 light-years across. Astronomers were surprised by the pictures, which reveal an unexpected haze of high-energy X-rays dominating the usual stellar activity.
"Almost anything that can emit X-rays is in the galactic center," said Perez, according to the press release. "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."
Astronomers have four potential theories to explain the baffling X-ray glow, three of which involve different classes of stellar corpses. When stars die, they don't always go quietly into the night. Unlike stars like our sun, collapsed dead stars that belong to stellar pairs, or binaries, can siphon matter from their companions. This zombie-like "feeding" process differs depending on the nature of the normal star, but the result may be an eruption of X-rays.
Alternatively, the source of the high-energy X-rays might not be stellar corpses at all, astronomers say, but rather a diffuse haze of charged particles, called cosmic rays. The cosmic rays might originate from the supermassive black hole at the center of the galaxy as it devours material. When the cosmic rays interact with surrounding, dense gas, they emit X-rays.
"This new result just reminds us that the galactic center is a bizarre place," said co-author Chuck Hailey, also from 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."
NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif., for NASA's Science Mission Directorate in Washington D.C.
