Study: ‘Black widow’ pulsar is spotted devouring a dwarf star

Researchers scrutinize Black Widow pulsar
Researchers scrutinize Black Widow pulsar

They observed 2 intense regions of radiation on this rapidly spinning pulsar some 6,500 light-years away. “Like seeing a flea on the surface of Pluto,” they said.

Researchers have taken one of the highest resolution observations ever, giving us the clearest look yet at a distant pulsar, a pulsating type of neutron star. The object, known as PSR B1957+20, is one of the heaviest pulsars known, and studying it will help us understand how matter behaves at the highest densities.

As reported in Nature, the team was able to observe two regions of intense radiation that were just 20 kilometers (12 miles) apart. Given that the pulsar is about 6,500 light-years away, this is the equivalent to spotting a flea on the surface of Pluto from Earth.

The incredible observations were possible thanks to the unusual configuration of the system. The pulsar is orbited by a brown dwarf that is trailing gas behind, a bit like a comet’s tail. The plasma left in the dwarf’s wake acts as a lens, bringing these details into view.

“The gas is acting like a magnifying glass right in front of the pulsar,” lead author Robert Main, from the University of Toronto, said in a statement. “We are essentially looking at the pulsar through a naturally occurring magnifier which periodically allows us to see the two regions separately.”

The pulsar is spinning 600 times per second, and this extreme rotation is accompanied by two high energy beams, which are released by hot spots on the surface. The region observed by the researchers are associated with the beams.

Their work here, however, expands beyond the nature of pulsars and extremely dense matter. It can also help us understand Fast Radio Bursts, extremely powerful and extremely brief emissions of radio waves from extragalactic sources.

“Many observed properties of FRBs could be explained if they are being amplified by plasma lenses,” said Main. “The properties of the amplified pulses we detected in our study show a remarkable similarity to the bursts from the repeating FRB, suggesting that the repeating FRB may be lensed by plasma in its host galaxy.”

PSR B1957+20 is also known as a black widow pulsar because scientists believe that it will soon cause the destruction of its companion. The pulsar could be between 1.7 and 2.4 times the mass of our Sun compressed into a region only tens of kilometers across. The brown dwarf is larger in size but smaller in mass, and orbits just 2 million kilometers (1.2 million miles) away from the pulsar.

Being so close, the brown dwarf is tidally locked, so one side of it is constantly being pummeled by intense radiation. This is enough to increase the temperature of that side to the temperature of the Sun. This process might eventually erode material from the dwarf and disintegrate it.


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