Scientists have been able to locate where particles in the vicinity of the rotating neutron-star in the Crab Nebula are accelerated to immense energies, thanks to data from the European Space Agency’s (ESA) Integral gamma-ray observatory. Resulting from more than 600 individual observations of the nebula, this discovery puts into place another piece of the puzzle in understanding how neutron stars work. Rotating neutron-stars, or pulsars, are known to accelerate particles to enormous energies. They are, typically, 100x more than the most powerful accelerators on Earth. However, scientists are still uncertain exactly how these systems work and where the particles are accelerated. A step forward in this understanding has now been accomplished, thanks to a team of researchers from the U.K. and Italy, led by Professor Tony Dean of the University of Southampton, who studied high-energy polarized light emitted by the Crab Nebula, one of the most dramatic sights in deep space.
The Crab Nebula is the result of a supernova explosion which was seen from Earth on July 4th, 1054. The explosion left behind a pulsar with a nebula of radiating particles around it and contains the mass of the Sun squeezed into a volume of about 10 km radius, rotating very fast at about 30 times a second. This generates extremely powerful magnetic fields and accelerating particles. A highly collimated jet, aligned with the spin axis of the pulsar and a bright radiating ‘donut’ structure (or torus) around the pulsar itself. Looking into the heart of the pulsar with Integral‘s spectrometer (SPI), the researchers made a detailed study to assess the polarization, or the alignment, of the waves of high-energy radiation originating from the Crab. They saw that this polarized radiation is highly aligned with the rotation axis of the pulsar. The conclusion is 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, most 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.
