First gamma-ray pulsar found outside Milky Way galaxy

TOULOUSE, France, Nov. 13 (UPI) -- A newly discovered pulsar, called PSR J0540-6919, is the first gamma-ray pulsar to be found outside the Milky Way galaxy.

The pulsar, which was imaged by NASA's Fermi Gamma-ray Space Telescope, is also the most luminous gamma-ray pulsar astronomers have ever seen.

The newly discovered pulsar is 163,000 light-years away from our solar system, located on the outer edge of the Tarantula Nebula, an oft-studied region of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way.

The Tarantula Nebula is so frequently studied because it's one of the closest and most active star-forming regions. In fact, scientists have known about this impressive source of gamma rays for some time. But until now, astronomers had misunderstood the source.

Scientists thought the gamma rays were the result of subatomic particles colliding in the wake of violent supernova explosions. The bursts are not a cumulative effect, it turns out. They are generated by a singular source.

"It's now clear that a single pulsar, PSR J0540-6919, is responsible for roughly half of the gamma-ray brightness we originally thought came from the nebula," lead scientist Pierrick Martin, an astrophysicist at the National Center for Scientific Research (CNRS) and the Research Institute in Astrophysics and Planetology in Toulouse, France, said in a press release. "That is a genuine surprise."

Researchers announced the newly discovered gamma-ray pulsar in a paper published in the journal Science.

J0540 is one of two pulsars identified within the Tarantula Nebula. The other is PSR J0537−6910.

Pulsars are a type of neutron star left in the wake of a supernova -- a star that, having collapsed in on itself, is extremely condensed. These stars rotate rapidly, and as they do their spinning electromagnetic field shoots out pulses of energy in the form of radio waves, visible light, X-rays and gamma rays.

J0540 is 20 times more powerful than the next most luminous gamma-ray pulsar. Researchers believe the pulsar's unusually young age has something to do with its power. J0540 is roughly 1,700 years old. Of the 2,500-plus pulsar identified by astronomers, the vast majority are 10,000 to hundreds of millions of years old.

"Accounting for these differences will guide us to a better understanding of the extreme physics at work in young pulsars," said study co-author Lucas Guillemot, an astronomer at CNRS and the University of Orleans in France.