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 be a congruence; that is, for the infinite unit distance graph whose vertices are all the points in the plane, any graph automorphism must be an isometry . The definition of a unit distance graph may naturally be generalized to any higher-dimensional Euclidean space. Any graph may be embedded as a set of points in a sufficiently high dimension; show that the dimension necessary to embed a graph in this way may be bounded by twice its maximum degree. The dimension needed to embed a graph so that all edges have unit distance, and the dimension needed to embed a