The first evidence for three-dimensional spin-velocity alignment in
  pulsars
  More than 50 years after the discovery of pulsars and confirmation of their
association with supernova explosions, the origin of the initial spin and
velocity of pulsars remains largely a mystery. The typical space velocities of
several hundred km/s have been attributed to "kicks" resulting from asymmetries
either in the supernova ejecta or in the neutrino emission. Observations have
shown a strong tendency for alignment of the pulsar space velocity and spin
axis in young pulsars but, up to now, these comparisons have been restricted to
two dimensions. We report here the first evidence for three-dimensional
alignment between the spin and velocity vectors, largely based on observations
made with the Five-hundred-meter Aperture Spherical radio Telescope of the
pulsar PSR~J0538+2817 and its associated supernova remnant S147. Analysis of
these and related observations has enabled us to determine the location of the
pulsar within the supernova remnant and hence its radial velocity. Current
simulations of supernova explosions have difficulty producing such
three-dimensional alignment. Our results, which depend on the unprecedented
sensitivity of the new observations, add another dimension to the intriguing
correlation between pulsar spin-axis and birth-kick directions, thus deepening
the mysteries surrounding the birth of neutron stars.
