Origin of high energy emission in Crab pulsar

Here's another wonderful press release on the origin of high energy emission from the Crab pulsar.

Using ESA’s Integral gamma-ray observatory, scientists (Professor Tony Dean of the University of Southampton and collegues) have been able to locate where particles in the vicinity of the rotating neutron-star in the Crab Nebula are accelerated to immense energies.

Rotating neutron-stars, or 'pulsars', are known to accelerate particles to enormous energies, typically one hundred times more than the most powerful accelerators on Earth, but scientists are still uncertain exactly how these systems work and where the particles are accelerated.

The Crab Nebula is the result of a supernova explosion which was seen from Earth on 4 July 1054. The explosion left behind a pulsar with a nebula of radiating particles around it. A highly collimated jet, aligned with the spin axis of the pulsar and a bright torus around the pulsar itself, are also seen. So, the Crab is known to accelerate electrons - and possibly other particles - to extremely high speed, and so produces high energy radiation. But where exactly are these particles accelerated?

Looking into the heart of the pulsar with Integral’s spectrometer (SPI), the researchers made a detailed study to assess the polarisation – or the alignment - of the waves of high-energy radiation originating from the Crab.

They used data from more than 600 individual observations of the nebula, and saw that this polarised radiation is highly aligned with the rotation axis of the pulsar. So they concluded that a significant portion of the electrons generating the high-energy radiation must originate from a highly organised structure located very close to the pulsar, very likely directly from the jets themselves. The discovery allows the researchers to discard other theories that locate the origin of this radiation further away from the pulsar.