RCW 88 of a larger halo of fainter nebulosity extending perhaps out to 10 arcmin. The RCW catalogue states the Hα image size is 3'×2. RCW 88 is located about 3300 parsecs (10,000 light years) from us, though other estimates place this at a closer 1800±300 pc. or 1800±200 pc. Assuming the former distance and the diameter as 5'-6' across, finds by simple trigonometry the true size subtends a minimum of 5±1 parsecs (16±3 light-years.) This small emission nebula shows a mean radial velocity of −18 km.s, and is also a faint radio source that was identified by Lloyd Higgs in 1971.
Unit distance graph pairs might also be at unit distance apart. For instance, the Möbius-Kantor graph has a drawing of this type. According to this looser definition of a unit distance graph, all generalized Petersen graphs are unit distance graphs . In order to distinguish the two definitions, the graphs in which non-edges are required to be a non-unit distance apart may be called strict unit distance graphs . The graph formed by removing one of the spokes from the wheel graph "W" is a subgraph of a unit distance graph, but is not a strict unit distance graph: there is only one