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 graph so that the edges are exactly the unit distance pairs, may greatly differ from each other: the 2"n"-vertex crown graph may be embedded in four dimensions so that all its edges have unit length, but requires at least "n" − 2 dimensions to be embedded so that the edges are the only unit-distance pairs . It is NP-hard, and more specifically complete for the existential theory of the reals, to test whether a given graph is a unit distance graph, or is a strict unit distance graph . It is also NP-complete to determine whether a unit distance graph