PSR J1745-2900: Closest-Known Pulsar At The Heart Of Milky Way

Their research shows that magnetars like this one, lying in close proximity to a black hole, could perhaps be linked to the source of “fast radio bursts,” or FRBs. FRBs are high-energy blasts that originate beyond our galaxy but whose exact nature is unknown.

“Our observations show that a radio magnetar can emit pulses with many of the same characteristics as those seen in some FRBs,” Caltech graduate student Aaron Pearlman, who presented the results today at the 233rd meeting of the American Astronomical Society in Seattle, said in a press release.

“Other astronomers have also proposed that magnetars near black holes could be behind FRBs, but more research is needed to confirm these suspicions.”

Magnetars are a rare subtype of a group of objects called pulsars; pulsars, in turn, belong to a class of rotating dead stars known as neutron stars. They are thought to be young pulsars that spin more slowly than ordinary pulsars and have much stronger magnetic fields, which suggests that perhaps all pulsars go through a magnetar-like phase in their lifetime.

The magnetar PSR J1745-2900 is the closest-known pulsar to the supermassive black hole at the center of the galaxy, separated by a distance of only 0.3 light-years, and it is the only pulsar known to be gravitationally bound to the black hole and the environment around it.

Researchers also collected new details about the magnetar’s radio pulses and using the Deep Space Network’s largest radio antennas, they analyzed individual pulses emitted by the star every time it rotated, a feat that is very rare in radio studies of pulsars. Some pulses were stretched, or broadened, by a larger amount than predicted when compared to previous measurements of the magnetar’s average pulse behavior. Moreover, this behavior varied from pulse to pulse.

“We are seeing these changes in the individual components of each pulse on a very fast time scale. This behavior is very unusual for a magnetar,” says Pearlman. The radio components, he notes, are separated by only 30 milliseconds on average.

One theory to explain the signal variability involves clumps of plasma moving at high speeds near the magnetar. Other scientists have proposed that such clumps might exist but, in the new study, the researchers propose that the movement of these clumps may be a possible cause of the observed signal variability. Another theory proposes that the variability is intrinsic to the magnetar itself.

“Understanding this signal variability will help in future studies of both magnetars and pulsars at the center of our galaxy,” says Pearlman, who hopes – along with his colleagues – to use the Deep Space Network radio dish to solve another outstanding pulsar mystery: Why are there so few pulsars near the galactic center? Their goal is to find a non-magnetar pulsar near the galactic-center black hole.

“Finding a stable pulsar in a close, gravitationally bound orbit with the supermassive black hole at the galactic center could prove to be the Holy Grail for testing theories of gravity,” says Pearlman. “If we find one, we can do all sorts of new, unprecedented tests of Albert Einstein’s general theory of relativity.”