Cartoon depicting our proposed scenario for the formation of VRO 42.05.01 as discussed in Sect. 5.2. The progenitor of VRO 42.05.01 would have been travelling between media of two different densities, at a speed approximately 1.15 times the local sound speed in the ISM in the low-density region, creating a Mach cone of 120°. When the supernova explosion occurred, the ejecta would have expanded in the triangular cavity caused by the bow shock, and through the small cavity to the high-density region.