Unusual 'Howling Zombie Stars' May be at the Milky Way's Core

In a day and age where zombies can be regularly found on TV, the silver screen, and even in video games, it's easy to argue that they are anything but rare. But what about radioactive and howling space zombies? Peering into the heart of the Milky Way galaxy, that appears to be exactly what one of NASA's impressive space telescopes has found, the details of which are published in a recent study.

According to new findings reported in the journal Nature, NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) has spotted a mysterious glow of high-energy X-rays that scientists say could be the "howls" of dead stars as they feed on their stellar companions. These howls, it seems, are coming from the very center of our galaxy, where everything from young stars, to small black holes, to moats of dust, all swarm around the supermassive black hole known as Sagittarius A.

"Almost anything that can emit X-rays is in the galactic center," Kerstin Perez of Columbia University in New York, the lead author of the study, explained in a statement. "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." (Scroll to read on...)

The astronomer added that there are several theories that can explain for such an intense wave of X-rays, three of which have to do with still-active stellar "corpses." We all know that when stars die, they often go supernovae, exploding in a blaze of glory. However, not every deceased star knows when to call it quits. Collapsed dead stars that belong to stellar pairs, for instance, 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- or even gamma-radiation.

NuSTAR has long been designated as the "zombie hunter" of NASA's arsenal ever since the small X-ray telescope was launched into space in 2012. It is the first telescope capable of capturing crisp images even in regions flooded with X-rays, like the Milky Way's core.

It was observations from this specialized space telescope that allowed Perez and her colleagues to theorize that their mysterious X-ray signaling could be the "howls" of some unusually powerful pulsars - a class of stellar zombie that spins exceptionally fast, sending out beams of radiation in the process. (Scroll to read on...)

"We may be witnessing the beacons of a hitherto hidden population of pulsars in the galactic center," added co-author Fiona Harrison of the California Institute of Technology (Caltech) in Pasadena, and principal investigator of NuSTAR. "This would mean there is something special about the environment in the very center of our galaxy."

However, that's not the only type of zombie star that warrants suspicion. According to the study, the unique high-energy X-rays that NuSTAR is detecting could be coming from exceptionally dense white dwarf stars - the remnants of a collapsed and burnt out star that was never large enough to climax into a supernovae in its last moments of life. It's interesting to note that our own Sun is such a star - doomed to simply fizzle out rather than ending things with a bang.

Still, that's not to say white dwarves don't have an interesting afterlife. Exceptionally dense ghosts of their former selves, they have stronger gravity and can radiate higher-energy X-rays than ever achieved as a living star.

"We can see a completely new component of the center of our galaxy with NuSTAR's images," said Perez, "[but] we definitively explain the X-ray signal yet -it's a mystery. More work needs to be done."

"This new result just reminds us that the galactic center is a bizarre place," added 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."

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