The Case of the Neutron Star With a Wayward Wake
This wide-field composite image was made with X-ray (blue/ROSAT & Chandra), radio (green/Very Large Array), and optical (red/Digitized Sky Survey) observations of the supernova remnant, IC 443. The pullout, also a composite with a Chandra X-ray close-up, shows a neutron star that is spewing out a comet-like wake of high-energy particles as it races through space.
Based on an analysis of the swept-back shape of the wake, astronomers deduced that the neutron star known as CXOU J061705.3+222127, or J0617 for short, is moving through the multimillion degree Celsius gas in the remnant. However, this conclusion poses a mystery.
Although there are other examples where neutron stars have been located far away from the center of the supernova remnant, these neutron stars appear to be moving radially away from the center of the remnant. In contrast, the wake of J0617 seems to indicate it is moving almost perpendicularly to that direction.
One possible explanation is that the doomed progenitor star was moving at a high speed before it exploded, so that the explosion site was not at the observed center of the supernova remnant. Fast-moving gusts of gas inside the supernova remnant may have further pushed the pulsar's wake out of alignment. An analogous situation is observed for comets, where a wind of particles from the Sun pushes the comet tail away from the Sun, out of alignment with the comet's motion.
If this is what is happening, then observations of the neutron star with Chandra in the next 10 years should show a detectable motion away from the center of the supernova remnant.