Crab nebula’s neutron star is pulsing with gamma rays

The Crab Nebula is a pretty strange crustacean. It’s a supernova remnant, from a supernova whose detonation was seen on Earth in 1054 CE. The explosion left behind a rapidly spinning neutron star and a large quantity of ejected matter that’s still expanding away from the blast site – and putting on an impressive show in optical and many other wavelengths.

Last year and earlier this year there were reports, based on detection by satellite observatories, of occasional very high-energy gamma-ray flares, cause unknown, having energies of at least 1015 eV. These are the highest energy particles detected in a discrete source, and the mechanism of their acceleration is unclear. (See here, here.)
And now very high-energy gamma-ray pulses – less energetic than the flares, but still with energies up to 400 GeV – have shown up, associated with the central pulsar itself, which spins and pulses about 30 times per second. Normally, energetic X-ray and gamma-ray photons are generated from high-speed charged particles in a strong magnetic field, by the process of synchrotron radiation (also known as “curvature radiation”). But that appears to be ruled out in this case, since the energy limit on gamma rays that could be ...