A radio-emitting X-ray "bullet" ejected by the Vela supernova

Abstract

A MASSIVE star that explodes as a supernova produces an expanding remnant—a shell of gas—and leaves behind a neutron star. It has been suggested that instabilities during these explosions may create high-density clumps of ejecta^1,2, but such fragments have never been found in a remnant containing a pulsar. Here we present X-ray and radio observations of a feature outside the shock-wave boundary of the Vela supernova remnant (associated with the pulsar PSR0833 – 45), which appears to be an ejected fragment, with a wake³. The feature, which has travelled nearly 50 pc from the site of PSR0833 - 45 but is only one parsec across, is a clear-cut case of a bullet of ejecta moving supersonically through the surrounding medium. The radio observations show non-thermal emission along the leading edge of the X-ray feature, indicating particle acceleration at the fragment's shock front.