|Figure 10 from authors: Q. Daniel Wang and Eric V. Gotthelf (1998)
some text from the paper with added emphasis and explanation:
"Such a relatively fast moving young pulsar [star leftover after a supernova explosion] can produce a strongly elongated pulsar wind bubble (Fig. 10). This bubble consists of several distinct regions. First, one may expect a bow shock running ahead of the pulsar, while the corresponding reverse shock terminates the free pulsar wind. The size of the region enclosed by this bow shock can be small, but the pressure can be large, depending on the ram pressure.
Enhanced synchrotron radiation can then make the region especially bright in the X-ray region. Second, accelerated by the pressure gradient between the bow shock and the ambient medium, the shocked wind materials, which are relativistically hot, naturally forms a supersonic jet inside a tunnel in the opposite direction of the pulsar's motion (Wang, Li, & Begelman 1993). Third, the jet likely shoots through the bubble and then induces another bow shock (or a series of oblique shocks) on the other side. Fourth, the terminated wind materials are forced back to the bubble, where most of the pulsar spin-down luminosity is dumped. Let us now examine this picture in a more quantitative way."