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PSR J0540-691: The First Extragalactic Pulsar Discovered by NASA

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PSR J0540-691: The First Extragalactic Pulsar Discovered by NASA

By analyzing data from NASA’s Fermi Gamma-ray Space Telescope, a group of researchers have found the first gamma-ray pulsar beyond our galaxy, called PSR J0540-691, the extraordinary object sets a new record of being the most luminous gamma-ray pulsar ever found to date.

PSR J0540-691 is located outside the Tarantula Nebula in the Milky Way’s small galactic neighbor, a dwarf galaxy called the Large Magellanic Cloud, found at about 160,000 light years away. The Tarantula Nebula is the largest and most active star-forming region in our galactic community. It is so frequently studied by astronomers because it identified as a bright source of high-energy forms of light – gamma-rays. Astronomers have so far misunderstood the source of these high energy particles. Initially, they attributed this glow to collisions of subatomic particles accelerated in the wake of violent supernova explosions.

It’s now clear that a single pulsar, PSR J0540-691, is responsible for roughly half of the gamma-ray brightness we originally thought came from the nebula,

said Pierrick Martin ~ lead author of the study published in the journal Science.

That is a genuine surprise.

So, what is a pulsar? The formation of a pulsar is very similar to that of a neutron star. When a massive star with 4 to 8 times the Sun’s masses reaches the end of its life, it explodes as a supernova, the outer layers are blasted off into space, if they don’t collapse into black holes (they’re less massive ~ between 1.4 and 3.2 sun’s masses) they can leave behind incredibly dense cores called neutron stars. This relatively tiny, super dense object, rotates tens of times each second and emits a powerful blast of radiation along its magnetic field lines. If the beams are pointing right at Earth, then astronomers see these pulses as regular flashes in the sky, and the object is classified as a pulsar. So, pulsars are simply rapidly-spinning neutron stars.

J0540 is 20x 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.

The gamma-ray pulses from J0540 have 20 times the intensity of the previous record-holder, the pulsar in the famous Crab Nebula, yet they have roughly similar levels of radio, optical and X-ray emission,

said study co-author Lucas Guillemot.

Accounting for these differences will guide us to a better understanding of the extreme physics at work in young pulsars.

 

 

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